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Username Post: 89 Cavalier V6, seeking advice        (Topic#354228)
Chew N Tobacca 
Poster
Posts: 22

Age: 36
Loc: Idaho
Reg: 05-14-14
12-05-18 06:21 PM - Post#2753528    

Hi all,

Searching for suggestions on my Cavalier. It's an 89 Z24 with the 2.8 V6 and 3-speed automatic (THM125C). Picked it up last year and have been fixing it up; somebody hack-and-slashed a bunch of stuff on it, and went through almost the entire engine. Finally got it running, now trying to figure out where I'm having stalling problems. Took it out for a decently long drive over the weekend, hoping it would smooth out after being driven a while. Plenty of low-speed accelerating and decelerating, as well as a bit of highway speeds. Didn't seem to change anything. To put it out there up front, I do use v6z24.com as a main source of information (though there's not much activity there any more). Thought I'd check with some of the experts here before I take the next step...

Here's the symptoms I'm experiencing. 1.) Starts right up without trouble, idles fine, but seems like it has an occasional miss until it starts to warm up. 2.) Will sit at idle as long as I let it. Once it warms up, idles nice but dies when you put it in gear, unless you give it two right feet to help the throttle. Such is the case in any forward gear or reverse. 3.) Seems like it takes exceptionally long to get to operating temp and the cooling fan to cycle on. My 96 Suburban with the Vortec 350 warms up considerably faster, which doesn't seem right. 4.) It does hesitate slightly when you mash on the throttle, but picks right up. 5.) Not throwing any codes to the ECM.

And the huge list of things I've done to it. I'll list mechanical parts as well as electrical. I have replaced: Timing chain and sprockets; oil pump with drive shaft and pickup screen; tranny fluid and filter; water pump and pulley; thermostat; nearly all the hoses and belt; thoroughly cleaned the entire intake including upper and lower manifolds and throttle body (which I took apart and cleaned and replaced the gaskets and o-rings); PCV valve; entire new air intake from the filter box to the throttle body. All the corresponding gaskets have also been changed.

There's probably more, but I'll start on the electrical side. Of the components I've replaced: MAP sensor; idle air control motor; temp sensor; oil pressure sender; the one fuel injector that didn't meet specs; TCC (lockup) solenoid; alternator and battery (checked all my cables, connections, and grounds); and of course, plugs and wires. All three coils and the ignition module were replaced shortly before I got it, as was the crank position sensor. I've also attempted the idle relearn as suggested by v6z24.com, but is difficult since it won't idle in gear.

I'm still struggling to figure out what's up. If any of you guys or gals have any ideas, any at all, I'm open for suggestions. Thanks for reading my long post, and thanks in advance for any feedback.

-Chew



 




Shepherd 
Frequent Contributor
Posts: 1786

Loc: Lake George, NY
Reg: 11-11-15
12-07-18 06:22 AM - Post#2753713    
    In response to Chew N Tobacca

Pretty tough to give any meaningful advice here, but, if stable idle is your base problem, check your tps setting at idle, should be about .5v also check the base idle set screw adjustment, both of these can skew idle stability. The ecu's back then were very unreliable, try tapping the ecu with a screwdriver handle when warmed up, see if the engine stumbles. I assume you have a 195t stat? Have you looked at whether the engine is going into closed loop?



 
Chew N Tobacca 
Poster
Posts: 22

Age: 36
Loc: Idaho
Reg: 05-14-14
12-07-18 06:25 PM - Post#2753790    
    In response to Shepherd

Thanks for your reply. I have not checked the TPS voltage, will do that. I have jiggled and wiggled the ECM (not banged on per say), with no change in anything. Yes, the thermostat is a 195. As far as checking for open/closed loop, how do I know for sure without a scantool or diagnostic equipment? I would imagine I would be triggering a code to the ECM if it were not?

Thanks again,
-Chew



 
Shepherd 
Frequent Contributor
Posts: 1786

Loc: Lake George, NY
Reg: 11-11-15
12-08-18 05:20 AM - Post#2753827    
    In response to Chew N Tobacca

Diagnostics back then were not very good. You need a basic obd1 scanner to look at this, should be plenty around, as most of these cars are gone.



 
Chew N Tobacca 
Poster
Posts: 22

Age: 36
Loc: Idaho
Reg: 05-14-14
12-17-18 06:30 PM - Post#2754869    
    In response to Shepherd

Sorry for the delay in my response. I did get my hands on a pretty top-notch scanner to dig a little deeper. I checked the TPS voltage at idle, and watched it as the engine warmed up; at idle it stayed steady at 0.69 volts, and when I gave it some throttle it increased to 0.92 at 2000 rpms, and roughly 12% throttle. Also, the scanner did confirm closed loop after idling for a little over 5 minutes. If I understand the DTC correctly, a code should only trigger a "high voltage" error on the higher end (closer to wide-open) reading compared to the maximum of roughly 5 volts. Again, I have no codes. Seems like I may want to investigate further; proportionally, that is a long way from the 0.45~0.5 volts that is typical. I will need to consult my service manual to double check the spec.



 
Chew N Tobacca 
Poster
Posts: 22

Age: 36
Loc: Idaho
Reg: 05-14-14
12-19-18 12:18 PM - Post#2755025    
    In response to Chew N Tobacca

I was reviewing some of the data I recorded while the engine was running, and the oxygen sensor readings caught my attention. The voltage reading to the sensor was never any lower than 448mV, and not above 533mV. Also, correct me if I am wrong, I believe the cross count should be somewhere around 3 and definitely under 10; the scantool recorded a brief low of 27, an approximate average of 108 or so, and a high of 237 (wtf!?). I'll stick a new sensor in there, once it's not raining, and report back with any results.



 
Chew N Tobacca 
Poster
Posts: 22

Age: 36
Loc: Idaho
Reg: 05-14-14
12-24-18 10:17 AM - Post#2755476    
    In response to Chew N Tobacca

Update...

Changed oxygen sensor. Fixed some driveability issues; I drove it around town a bit, symptoms still exist but not as bad. I hooked up the scan tool again to see the values from the o2 sensor, and no real difference in readings. But it did at some point trigger a code 43, electronic spark control / knock sensor circuit. Previous recorded data showed there was communication with knock sensor and spark timing was being adjusted. Now that I changed the o2 sensor, I no longer get anything but a zero reading from the knock sensor. Double checked the wiring to it, all seems intact. Will change it out when the snow is gone and report back again.



 
Chew N Tobacca 
Poster
Posts: 22

Age: 36
Loc: Idaho
Reg: 05-14-14
01-09-19 06:22 PM - Post#2756987    
    In response to Chew N Tobacca

Update. Knock sensor changed, along with pigtail for it while I was under there. Symptoms still persist. Took it for a two mile or so trip to the grocery store, all was well until I got back in after shopping and was a bear to get started again. I hadn't really thought of it until then, but made me question the EGR valve functionality. Feels a bit stiff, so I'm gonna grab a new set of gaskets for it and clean it up really good this weekend when I get the time. Will post back once more after that and a test drive.



 
Chew N Tobacca 
Poster
Posts: 22

Age: 36
Loc: Idaho
Reg: 05-14-14
01-24-19 05:11 PM - Post#2758143    
    In response to Chew N Tobacca

Progress has been made. With an unfortunate discovery...

I removed and cleaned the EGR valve, with no change. Even vacuum tested the valve and seemed to be working properly. After that I started to work backwards to try to detect potential misfire. Took my infrared thermometer to the exhaust manifolds, expecting to find one that was considerably off from the rest. Which I did. After warming up a few minutes, I got a consistent 170 F (+/-5) from cylinders 1-5 and a ridiculous 310-320 F out of number 6. I believe (please correct me if I'm wrong) this can only represent valve damage.



 
Shepherd 
Frequent Contributor
Posts: 1786

Loc: Lake George, NY
Reg: 11-11-15
01-27-19 09:41 AM - Post#2758274    
    In response to Chew N Tobacca

Try and check temps at head port, the manifolds unless header type design can be misleading. Try running some Chevron techron or Seafoam thru the fuel system, at that age the injectors could be dirty.



Edited by Shepherd on 01-27-19 09:46 AM. Reason for edit: No reason given.

 




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