scott88
Member
Posts: 5
Reg: 11-30-04
|
12-02-04 07:04 AM - Post#566005
I have an 88 Chevy C2500, 2WD with 350 TBI. I have a similar problem that I have been working on for 2 years and had a GM mechanic stumped for over a year. The engine runs smooth sometimes and runs horribly bad at others like it is severely out of time, backfiring through the throttle body.
I replaced timing chain, injectors, tune-up and fuel pressure regulator. The mechanic changed out the computer, distributor and checked the ignition and MAP sensors. The problem persists. It is part of the electronic ignition system because when I disconnect the ignition bypass wire, the engine runs fine, no hesitation, smooth, etc. and I plug it back together, it runs awful. My truck had symptoms years ago, such as not idling well and at times run bad, but run good after shutdown and restart.
If anyone has enlightenment on this situation, I would be grateful if you could share you knowledge with me. How do the ignition module, electronic spark control and ECM work together with engine sensors??
Thanks
|
|
ICON
Senior Member
Posts: 304
Loc: Western Mass
Reg: 09-01-04
|
Re: 88 350 TBI timing/ignition problem
12-02-04 09:19 AM - Post#566006
In response to scott88
Any ryhme or reason to the problem?? Happens hot or cold? Underload or idling? Was everything in Dist replaced w/new one?
| '01 Tundra SR5 4x4
'05 Honda Foreman 500 4x4
'96 Yamaha Waverunner III |
|
loudpedal
Super Senior Member
Posts: 5010
Loc: corner of Walk & Dontwalk...
Reg: 07-28-00
|
Re: 88 350 TBI timing/ignition problem
12-02-04 09:46 AM - Post#566007
In response to scott88
check the coil resistance values when warm
check the distributor pickup for shorting/intermittents.
Check the dist reluctor and the top portion of the reluctor for rust at the dist shaft area. This is a common problem spot.
Check grounds at the EST module.
|
scott88
Member
Posts: 5
Reg: 11-30-04
|
Re: 88 350 TBI timing/ignition problem
12-02-04 03:23 PM - Post#566008
In response to loudpedal
No ryhme or reason, sometimes it runs good when its cold, sometimes when hot. Runs bad about 90% of time. Seems to run good under steady state operation with a light load, as soon as you hit the gas quickly, it hesitates and sounds bad. If I go slow it is smooth. I drove it the other night and ran super, stopped and got gas, drove down the road and punched it and it started it again.
What I did notice is that if I bypass the ignition by disconnecting the connector, the hesitation and problems go away except for the effects of not having ignition advance.
|
scott88
Member
Posts: 5
Reg: 11-30-04
|
Re: 88 350 TBI timing/ignition problem
12-02-04 03:26 PM - Post#566009
In response to loudpedal
Where is the timing advance controlled? Ignition module, electronic spark control? I disconnected the knock sensor and nothing changed. Could it be a bad ignition module? What is anyone's opinion of Auto Zone's checks on ignition module? (accurate or not)
|
1983G20Van
Super Senior Member
Posts: 3875
Loc: Bedford, Texas, USA
Reg: 11-13-02
|
Re: 88 350 TBI timing/ignition problem
12-02-04 03:32 PM - Post#566010
In response to scott88
Check your tps voltage. It is the middle wire in the connector going to the throttle position sensor. With the key on, engine off back probe the connector with a DIGITAL multimeter (I CANNOT STRESS ENOUGH HOW IMPORTANT IT IS NOT TO USE ANALOG). You should get around .5 volts with the throttle closed. Slowly open the throttle while observing the meter. It should smoothly increase up to about 5 volts at wide open throttle. Another check you can do is check the MAP sensor. The map is the vacuum sensor (for lack of a better description). It should read about 3.5-4.5 volts with the engine off. With the engine idling the Map should put out about 1 volt. If you suddenly snap the throttle open it should go towards 3.5 or 4 volts followed by a reading of about .6 to .8 during decel (after blipping the throttle). It sounds like you possibly have a dead spot in one of your sensors.
The module checks are accurate as all they do is simulate the conditions in the vehicle. Just make sure that they run the test enough times to get the module warm. That takes 10-15 times, but one check takes about 15 seconds so it not that big a deal. I have seen alot of modules pass good when cool, but fail when warm. I do these checks all the time.
| 1983 G20 Van, 350 TPI, Ported 906 Vortecs, Edelbrock 3817 Base, ASM oversize runners. Reed Custom Roller cam, 700r4, 12 bolt with 3.08 gears, Doug Thorley Tri-Y headers, true duals |
|
355Cheyenne
Senior Member
Posts: 3790
Loc: Northern MN
Reg: 10-27-04
|
Re: 88 350 TBI timing/ignition problem
12-02-04 03:40 PM - Post#566011
In response to scott88
kind of an older engine. when I rebuilt my 88 I had a problem with nocking even though I timed perfectly and it turned out that my outer ring on my balancer slipped over time and so my timing mark was off considerably. could this be your problem too? that your not timing the engine right because the mark is off on the balancer?
you might be able to tell by lining up the paint chips on it from the outer ring to the center piece. also if you just try advancing and retarding the engine to see if it improves or worsens.
oh yeah and my Map sensor was givng 100% load as it was bad causing miss fires up the carb, running too rich. sounds like you should start frome square 1 and get your self a good gm fuel injection book and test each sensore and veryfy you have perfect timing.
Tom
| 98 Silverado k1500 4x4 350 |
|
jritland
Member
Posts: 14
Age: 72
Loc: Haines City, FL
Reg: 12-01-04
|
Re: 88 350 TBI timing/ignition problem
12-02-04 04:02 PM - Post#566012
In response to scott88
I have an 88 suburban that did the same to me. Left it parked for 6 months changing this and that, nothing helped.
It turned out to be the pickup coil. The coil checked good, using the meter test in the manual so it was not considered a cure and ignored. Finally a friend of mine told me to change it even if it did pass the meter test. $6.50 later for a new coil that fixed it made me a believer in changing the darn thing right off the bat in the future.
82 GMC 2wd P/U
86 S10 Blazer 4wd
88 & 89 2wd Suburban's
90 & 93 4wd Suburban's
90 K5 Blazer 4wd
94 2500 4wd P/U
95 2500 4wd Suburban
02 2wd ext cab P/U |
|
1983G20Van
Super Senior Member
Posts: 3875
Loc: Bedford, Texas, USA
Reg: 11-13-02
|
Re: 88 350 TBI timing/ignition problem
12-02-04 04:19 PM - Post#566013
In response to jritland
The distributer on his engine has already been changed as stated in his first post. That means the pickup coil too.
| 1983 G20 Van, 350 TPI, Ported 906 Vortecs, Edelbrock 3817 Base, ASM oversize runners. Reed Custom Roller cam, 700r4, 12 bolt with 3.08 gears, Doug Thorley Tri-Y headers, true duals |
|
jritland
Member
Posts: 14
Age: 72
Loc: Haines City, FL
Reg: 12-01-04
|
Re: 88 350 TBI timing/ignition problem
12-02-04 04:25 PM - Post#566014
In response to 1983G20Van
Then the question is, where did that dist come from? New or used? known for sure to be good? Everything else has also been changed that would have anything to do with timing.
82 GMC 2wd P/U
86 S10 Blazer 4wd
88 & 89 2wd Suburban's
90 & 93 4wd Suburban's
90 K5 Blazer 4wd
94 2500 4wd P/U
95 2500 4wd Suburban
02 2wd ext cab P/U |
|
1983G20Van
Super Senior Member
Posts: 3875
Loc: Bedford, Texas, USA
Reg: 11-13-02
|
Re: 88 350 TBI timing/ignition problem
12-02-04 05:08 PM - Post#566015
In response to jritland
Not saying that the pickup coil couldn't be bad but generally a bad pickup coil won't let the engine run(although a broken wire running from it will make the engine run very bad). The computer controls timing by using inputs from various signals. One bad sensor and the engine will run poorly. The ECM relys on look up tables cross referenced against inputs from the various sensor. Almost every sensor has an affect on advance. The map sensor plays a vital role in the timing advance. The "Main" spark table is just Map vs. RPM.
| 1983 G20 Van, 350 TPI, Ported 906 Vortecs, Edelbrock 3817 Base, ASM oversize runners. Reed Custom Roller cam, 700r4, 12 bolt with 3.08 gears, Doug Thorley Tri-Y headers, true duals |
|
jritland
Member
Posts: 14
Age: 72
Loc: Haines City, FL
Reg: 12-01-04
|
Re: 88 350 TBI timing/ignition problem
12-04-04 01:14 AM - Post#566016
In response to 1983G20Van
Very true about the pickup coil. If it has an open or broke wire it won
82 GMC 2wd P/U
86 S10 Blazer 4wd
88 & 89 2wd Suburban's
90 & 93 4wd Suburban's
90 K5 Blazer 4wd
94 2500 4wd P/U
95 2500 4wd Suburban
02 2wd ext cab P/U |
|
scott88
Member
Posts: 5
Reg: 11-30-04
|
Re: 88 350 TBI timing/ignition problem
12-04-04 11:54 AM - Post#566017
In response to jritland
Thanks to all who are helping me diagnose the problem. It is a new distributor that our mechanic installed. It has new pickup coil, module, etc.
I spent the entire day further diagnosing the problem. I had a timing light hooked up to the #1 cylinder and watched the advance as I would rev the engine. If I would rev the engine slowly, the timing would advance until it hit a certain RPM and then would suddenly severly retard (20 degrees BTDC). If I would punch the throttle, it would severly retard immediately. If I bypass the computer controlled advance, it runs good and does not miss a beat. I will doulbe check the MAP sensor, since that is the sensor that would provide input if the throttle is punched.
Thanks again everyone for all your help. Keep it coming.
What is the purpose of the Distributor HI and LO references to the computer? Can I measure the signal for advance from the computer with a Multimeter. Does the computer give a varying voltage signal to tell the ignition module how much advance to move.
The engine has (2) ground wires, a smaller one in the back and a larger one underneath toward the front. Could one of these be a problem. I did ground the engine with jumper cables and it did not make a difference.
Scott
|
Trevorhoward
Forum Newbie
Posts: 1
Reg: 07-27-12
|
07-27-12 08:27 AM - Post#2252677
In response to scott88
If your truck runs rough at idle and under a slight load it couls be the EGR sensor.Try unplugging the vacuum hose going to EGR valve if that works replace the egr sensor
|
Astro88
Forum Newbie
Posts: 49
Reg: 02-09-10
|
07-31-12 01:03 PM - Post#2254226
In response to Trevorhoward
Ok, I thought I'd ask in this post, since I'm dealing with an 88 TBI 350 C-Series truck, and am having an ignition/timing problem. On friday, my buddy was driving it, and it started to really loose power, and would hardly run at all. In fact it stalled twice on him. Saturday, he brought it out, and I took it for a test drive. Man it really ran like crap. So I unplugged the "timing lead", as I wanted to find out IF that had any real effect on it. It did, but not much. Anyway, I put a timing light on it, and found it to be about 1.5 inches below the timing mark, so we "re-set" the timing. It ran real good again. I should mention, that this truck had just been resurrected from sitting in a field for 10 years, and has had the engine gone thru, along with the fuel tank, fuel pump, and sending unit replaced, along with a new knock sensor and O2 sensor. In fact just the weekend prior, we put another set of plugs in it, as it was running rough (he thought it needed a set), but not like friday. Fast forward to yesterday, and it started acting up again, and the timing got re-set again, and an 89 brain was tossed in (thinking the rodent wiz (from sitting 10 years) might have messed up the original one). Everything was good until this afternoon, until it just completely quit running (not stalled, but just shut off). Is this a possible ignition pick up failure? We put the old brain back in, and the truck would idle, but under load is a no-go. He's ready to swap it over to a carb (we did this to his 93 2500 already), IF we can't figure out why it keeps changing timing on it's own (the distributor was locked down in place, and wouldn't move at first). Also, there are no codes being indicated, which is throwing us for a loop. It had been running good for the last 3 months, but now it's undriveable. Any help offered is appreciated, as I've kinda run out of ideas to check.
|
 someotherguy
Senior Moderator
Posts: 29396
Loc: Texas
Reg: 08-01-03
|
07-31-12 04:42 PM - Post#2254292
In response to Astro88
Are you checking (and setting) the timing with the tan/black wire disconnected - every time - 100% sure? If yes, and it's changing timing on you, 3 possibilities I can think of right off the bat, just be forewarned I woke up very recently 
1. Wiring harness damage
2. Ignition module going bad/intermittent
3. Harmonic balancer slipping (though this wouldn't explain the change in how it runs)
Richard
| 06 Silverado ISS / 06 Silverado SS / 06 300C SRT8 |
|
355Cheyenne
Senior Member
Posts: 3790
Loc: Northern MN
Reg: 10-27-04
|
07-31-12 06:47 PM - Post#2254332
In response to someotherguy
Not to be a jerk but WOW Zombie thread... Lets make a new thread. and I don't understand dumping decades of advancements for an older system because a part wears out and or fails in the system. I mean even if the distributor is just worn out, you would still need to swap that out to convert to carb, why not just fix the distributor? Also to add to the argument, likely the failure in the system now is still susceptible in a carb configuration.
| 98 Silverado k1500 4x4 350 |
|
Astro88
Forum Newbie
Posts: 49
Reg: 02-09-10
|
08-01-12 06:10 AM - Post#2254441
In response to someotherguy
Are you checking (and setting) the timing with the tan/black wire disconnected - every time - 100% sure? If yes, and it's changing timing on you, 3 possibilities I can think of right off the bat, just be forewarned I woke up very recently
1. Wiring harness damage
2. Ignition module going bad/intermittent
3. Harmonic balancer slipping (though this wouldn't explain the change in how it runs)
Richard
Yes, the tan/black wire is disconnected 100% of the time. It was reassembled last year, timing set, and was good up until about a week ago. Then it got re-set. I've been playing with these trucks and systems for about 10 to 15 years, and never had to re-set the timing on one. It's always been a set it and forget it deal. But...
1A)I suppose the wiring could be dammaged, but where would I look for it? It's still in the factory convoluted tubing, and it's not throwing any codes.
2A) I've always had them either work, or be dead. I've even had them die while backing out of the garage before.
3A) I had thought about that, but I don't see any evidence of it slipping. Re-setting the timing Saturday, brought the truck back to life, and ran great to and from the beer store. Something moved, but what? And why?
|
Astro88
Forum Newbie
Posts: 49
Reg: 02-09-10
|
08-01-12 06:26 AM - Post#2254446
In response to 355Cheyenne
Not to be a jerk but WOW Zombie thread... Lets make a new thread. and I don't understand dumping decades of advancements for an older system because a part wears out and or fails in the system. I mean even if the distributor is just worn out, you would still need to swap that out to convert to carb, why not just fix the distributor? Also to add to the argument, likely the failure in the system now is still susceptible in a carb configuration.
I'm on other forums as well as this one, and I was just trying to use proper forum protocol (by adding to this current existing thread), otherwise I would have started a new thread.
It's NOT my truck, so I can't dictate what the owner can, or wants to do (other than fix it). This is his company work truck (he's self employed) and can't afford the down time sitting along side the road (not making any money).
I was just asking IF the problem could be the pick up coil, as the timing is changing on it's own. I've NEVER had a GM do that before! The engine itself is a 350HP 350 crate engine, so I doubt the timing chain (or gears) is worn out (causing a jumping in time). I listed above what some of the parts were that have been replaced in the last year (with some in the last 4 months). The rest of the components are OE 88 chevy. He'd really like to keep the FI, but IF it's going to keep leaving him stuck alongside the road, it WILL get converted (he's already told me this 4 times). I'm going over there later today, and swapping out the entire distributor (I've got 1 here), and I'm taking a spare ESC unit, along with a couple of other electronic parts (TCS,TPS, MAP, etc...), to see IF I can fix it.
Thanks for the help.
Edited by Astro88 on 08-01-12 06:30 AM. Reason for edit: No reason given.
|
 62chevy427
"14th Year" Silver Supporting Member
Posts: 2200
Loc: laurens sc
Reg: 04-13-06
|
08-01-12 06:39 AM - Post#2254451
In response to scott88
just for kicks,check the egr valve for proper opening,closing
56 bel air ((since 2002)
62 impala ss (since 1965)
65 el camino (since 1969)
66 nova (since 1987)
67 malibu convertible (since 1981)
72 el camino ss454 (since 1985)
83 gmc 4wd (since 1991)
95 impala (new)
15 chevy equinox
|
|
Astro88
Forum Newbie
Posts: 49
Reg: 02-09-10
|
08-01-12 06:47 AM - Post#2254460
In response to 62chevy427
just for kicks,check the egr valve for proper opening,closing
I saw that above too, and I'm taking my vacuum pump to check it as well.
|
355Cheyenne
Senior Member
Posts: 3790
Loc: Northern MN
Reg: 10-27-04
|
08-01-12 07:25 AM - Post#2254470
In response to Astro88
Not to be a jerk but WOW Zombie thread... Lets make a new thread. and I don't understand dumping decades of advancements for an older system because a part wears out and or fails in the system. I mean even if the distributor is just worn out, you would still need to swap that out to convert to carb, why not just fix the distributor? Also to add to the argument, likely the failure in the system now is still susceptible in a carb configuration.
I'm on other forums as well as this one, and I was just trying to use proper forum protocol (by adding to this current existing thread), otherwise I would have started a new thread.
It's NOT my truck, so I can't dictate what the owner can, or wants to do (other than fix it). This is his company work truck (he's self employed) and can't afford the down time sitting along side the road (not making any money).
I was just asking IF the problem could be the pick up coil, as the timing is changing on it's own. I've NEVER had a GM do that before! The engine itself is a 350HP 350 crate engine, so I doubt the timing chain (or gears) is worn out (causing a jumping in time). I listed above what some of the parts were that have been replaced in the last year (with some in the last 4 months). The rest of the components are OE 88 chevy. He'd really like to keep the FI, but IF it's going to keep leaving him stuck alongside the road, it WILL get converted (he's already told me this 4 times). I'm going over there later today, and swapping out the entire distributor (I've got 1 here), and I'm taking a spare ESC unit, along with a couple of other electronic parts (TCS,TPS, MAP, etc...), to see IF I can fix it.
Thanks for the help.
I was just blown away because this thread dated back to 2004 and that was the last posting from the OP. The point to making a new thread is so that people don't get confused or lost in someone elses issues and trouble shooting. For example they may not offer advice because it was already offered to the other guy but they did not realize you had or had not tried it or if it was you or not. The fact that your user names are very similar adds to the confusion.
I know I am not helping by being picky but I am just saying and I am sorry if I am sounding like a turd, I am just saying that I think you could be better helped with a fresh new thread.
Anyway I think you will be set with what you are planning, new distributor and ESC. The only thing that could be a wrench in your work is the balancer may have slipped over time. It is hard to determine if they have slipped but sometimes you can look at paint chips and see they don't line up which can be an indication. Otherwise you need to get #1 to TDC by removing the spark plugs and using a coat hanger or something similar to confirm you are at TDC and then see if the line is lining up to zero degrees.
| 98 Silverado k1500 4x4 350 |
|
FLTCM
Forum Newbie
Posts: 5
Reg: 08-11-12
|
09-18-12 09:41 AM - Post#2270920
In response to Astro88
My 88 Sub TBI 350 had the exact symptoms. Problem - It was a 3/4 inch split in the two inches of fuel line that connect the pump to the fuel system inside the fuel tank. Less than 1/4 inch of actual hole in the 3/4 inch split, because part of the split was on the connecting tube to the pump. Leading to the problem becoming a constant one was -lagging power, then idle cycled up and down continually until the engine got hot, then it idled high. Sometimes the 88 ran fine for a while, then lagged power. Shut it down and cool it for a while and it ran good again for a bit. But progressively got worse until it was not drivable. Code 44 then 22, 33 as I changed parts. Changed the MAP, TPS, IAC, PCV, O2 sensor, cleaned the EGR, reseated all wires and giggle tested, new plug wires, dist cap and rotor, coil, rebuilt the TBI, removed the catalytic converter and muffler (straight pipe), new intake manifold gaskets, new vac hoses, redid all grounds and, finally, changed the fuel pump and found the split. Pump is good, but changed it out while in there. Took 2 full months, probably 150 man hours, easy. Real ball buster.
|
Jake_42022
Forum Newbie
Posts: 16
Loc: Tampa Florida
Reg: 09-14-12
|
09-18-12 02:21 PM - Post#2271001
In response to scott88
I would replace the igintion coil for sure very cheap sounds like a sensor is gone bad but works some of the time so it doesnt come on the ECU if ur SES light is on check the codes for goodness sake but if ur car struggles when u mash the gas i would look into the igintion coil and go double check all ur sparkplug wires and make sure they are plugged in securely in the dist. and sparkplugs
|
|
|
|
Report Post
Quote Post
Quick Reply
|
|
Print Topic
Email Topic
67181 Views
|
|
|
Gain extra benefits by becoming a Supporting Member 
