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Username Post: 89 G20 - fast idle and misfire in top gear        (Topic#308626)
89-G20shopvan 
Forum Newbie
Posts: 4

Loc: Banjo Country - South Swe...
Reg: 02-24-14
02-24-14 03:18 AM - Post#2429911    

Hi CT - nice forum

I'm a Brit living in Sweden - total gas head - lots of space out here so I have room to build my own junk yard.

Here's my question please:

1989 G20 standard van - 350 SBC, 700R4 box

Been running perfectly until my lovely lady left the lights on and found it hard to start. Now I don't know if she flooded it by continuously pumping the pedal while turning it over with the remaining juice in the battery...

But when I turned up with the support car and jumped the batteries together, the van just turned and turned with no fire happening at all.

I whipped the dog house off and could smell gas more than I thought reasonable.

So I took a couple of plugs out and they where soaking no surprise.

So I took the back 3 out of each bank (it was freezing cold over here and I was not keen to snap off my fingers getting the front plugs out ;). Dried them off and disconnected the power to the injectors and hit the tit.

She rumbled around spitting gas vapour out of the open holes and then fired up on 2!!

She used all the spare gas then died.

Cool I thought! All dried up and ready to put back together.

Injector leads on, plugs in.

Hit the key - fired no problem.

Job done or so I thought.

A week or so later, I hadn't run the van, I needed to get her ready for the Swedish yearly test. I ran it to the gas station to get her warm and try all the lights brakes etc. and while leaving her at idle in park, she started racing (I guess 2000rpm ish). When I selected reverse she stalled and wouldn't start for love nor money.

Went back next day - started perfectly.

Test drove yesterday, takes a lot of turning to start, when started stutters and picks up repeatedly until a bit warmer.

When driving engine sounds like idle is high when you coast in gear.

Carried on driving, got misfire under load when accelerating.

Also in top, pushed accelerator gives misfire/backfire.

So I've just jumpered AB on the OBD1 block - and got a 12 and 15.

15 is Engine Coolant Temp isn't it?

Any tips on where to check:

HT leads (given I'd moved them all from laying dormant for ages)
TBI (because I pulled the power connects off)


Your help is appreciated thanks

Steve
Do it now, because later soon becomes never


 
someotherguy 
Moderator
Posts: 25580
someotherguy
Age: 44
Loc: Texas
Reg: 08-01-03
02-24-14 07:22 AM - Post#2429947    
    In response to 89-G20shopvan

Welcome to Chevytalk, Steve,

The code 15 is your smoking gun. Check out your coolant temperature sensor and its connector in the harness; it's the one next to the thermostat housing. These often go bad enough to cause problems like this and still never set a code, so the fact that you got the code is pretty clear evidence of a problem with that sensor or its circuit.

Also check out the harness grounds at and next to the thermostat housing. These need to be in top notch shape.

Richard
94 C2500LD / 94 C1500 / 06 300C SRT8
Check out my truck shop projects


 
89-G20shopvan 
Forum Newbie
Posts: 4

Loc: Banjo Country - South Swe...
Reg: 02-24-14
02-24-14 08:03 AM - Post#2429961    
    In response to someotherguy

Thanks Richard - I'll check out the suspect parts and post back.

Steve
Do it now, because later soon becomes never


 
89-G20shopvan 
Forum Newbie
Posts: 4

Loc: Banjo Country - South Swe...
Reg: 02-24-14
02-24-14 10:15 AM - Post#2430009    
    In response to 89-G20shopvan

Hey (SomeOtherGuy) Richard!

I just had an hour to spare so I wrestled the ECT sensor out of my spares Beauville (it's got a/c so it was not as easy, and the thing was tight as...)

Anyway, swapped into the G20.

Started exactly as she has done prior to misfiring! Great!

Took her for a 25 minute run - all seemed fine until turning around halfway, started to hesitate at low revs.

SES light went off part way on first half, came back on and off a few times.

Kick down and acceleration 3rd to 4th is without too much hesitation and she runs at 65 70mph smoothly.

Slow speeds experience erratic misfires and a couple of stalls while parking back home.

Started up 3 or 4 times without too much worry.

So I gave a her a load of gas in park.

SES light is out.

Tickover seems ok but I'll check again tomorrow.

Thanks so much - regards Steve
Do it now, because later soon becomes never


 
someotherguy 
Moderator
Posts: 25580
someotherguy
Age: 44
Loc: Texas
Reg: 08-01-03
02-24-14 11:00 AM - Post#2430022    
    In response to 89-G20shopvan

I know it's a pain but since you're planning on doing the spark plug wires soon, you might well do the plugs or at least remove, clean, and check the gaps. It doesn't take long to fuel-foul the plugs when the CTS is really bad. I also wouldn't trust a used CTS even if it was behaving properly in another vehicle; sounds like it was an effective test but I'd get a quality brand new one (AC Delco or Delphi) ASAP. Also AC Delco on the plugs by the way; these TBI engines like the original equipment type CR43TS. They can be picky about "fancy" plugs like Bosch +4's or any of the gimmicky plugs like E3's.

Richard
94 C2500LD / 94 C1500 / 06 300C SRT8
Check out my truck shop projects


 
CowboyTrukr 
"3rd Year" Silver Supporting Member
Posts: 1732
CowboyTrukr
Loc: Salt Lake City
Reg: 06-20-09
02-24-14 11:02 AM - Post#2430023    
    In response to 89-G20shopvan

What codes do you have now?

Greg
'94 Silverado K2500 4X4 5.7 5spd Xcab LB. SOLD. :-(
'00 Contour SE 2.5 24V

"The only thing necessary for evil to triumph is for good men to do nothing" Sir Edmund Burke


 
89-G20shopvan 
Forum Newbie
Posts: 4

Loc: Banjo Country - South Swe...
Reg: 02-24-14
02-25-14 12:08 AM - Post#2430256    
    In response to CowboyTrukr

Hi - just checked the codes before I go out to the day job

12
15 32 33 45

Seems like ECT again
Exhaust gas and Manifold pressure plus
Rich running

.... opening up the can of worms now I guess

Your guidance is appreciated thanks.

/Steve
Do it now, because later soon becomes never


 
someotherguy 
Moderator
Posts: 25580
someotherguy
Age: 44
Loc: Texas
Reg: 08-01-03
02-25-14 05:05 AM - Post#2430274    
    In response to 89-G20shopvan

MAP sensor almost never goes bad on these; check that its vacuum line is firmly connected. It attaches at the middle rear of the TBI via a plastic line with a rubber boot. The boot often hardens up, cracks, doesn't seal well - or simply gets knocked off. This will cause a rich condition.

As I said don't trust the used CTS. Replace with new. Then check those grounds. The other errors are likely caused by the CTS issue. The EGR may very well have a problem but you won't know for sure until you fix the CTS first, clear codes, and drive it a bit to see what codes come back, if any.

Richard
94 C2500LD / 94 C1500 / 06 300C SRT8
Check out my truck shop projects


 
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