1988 Chevrolet Cavalier Z24 Surging

Mr.1980

Mr.1980

n00b
Feb 27, 2018
4
0
1
East Providence, Rhode Island
#1
Now before I explain the problem I admit yes this is a J-Body GM, but I have 2 other G-Bodies and have had good luck with this forum in the past. The car in question is a 1988 Chevrolet Cavalier Z24 Convertible, with a 2.8L direct fuel injected engine with a little over 106,000 miles on it. About 2 weeks ago I pulled out of my driveway and went about a quarter of mile down the road and stopped at a stop sign, the car had a very rough idle surged very high and stalled out, I shifted into park and tried starting the engine it consistently cranked over but would not engage. So I had AAA tow the car to my shop, we replaced the fuel filter and cleaned out the Throttle Body it had a slight improvement, we replaced the Throttle Position Sensor adjusting it to factory GM spec voltage it made a slight improvement again.

Today we replaced the Idle Air Control Valve which upon removal found the old IAC to be sticking and loaded with carbon build up and the vehicle had a real big improvement in overall performance and idle surging reduced after replacing the IAC valve. However it still has a very small surge from idle but much less than originally. When I pulled the vehicle out of the garage and into the shop parking lot, I drove it around and simulated a stop at a stop sign when I did that it idled a little rough and stalled out; however this time when I put it in park and attempted to restart the engine it started up relatively easier than when this first started a few nuna, nuna, nuna and it kicked over shifted into drive and drove fine. I simulated this stop sign scenario again, and again it stalled out at a complete stop from a hesitant idle shifted into park and restarted the engine again with a few nuna, nuna, nuna and it turned over I parked it and have now returned to the drawing board. I suppose it could be clogged or dirty fuel injectors but I don't think it's a fuel related problem because as long as the car doesn't come to complete stop the engine won't stall.

The part I cannot understand is regardless of the fact that this car is OBD1 it hasn't thrown any kind of code, neither before or after any repairs. Only a check engine light when it stalls, after it restarts no lights, no codes. I have a GM Tech 1 but the ECM doesn't give me any troubleshooting codes to read or work with. This particular engine even though it has a Throttle Body does not have a Mass Air Flow Sensor so that rules that out, I already replaced the Idle Air Control Valve, Throttle Position Sensor, and Fuel Filter which all have made a significant improvement in overall performance but haven't solved the stalling at idle at a complete stop. So any thoughts would be greatly appreciated. Thanks
 
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DRIVEN

DRIVEN

Comic Book Super Hero
Apr 25, 2009
4,818
1,924
113
Owyhee County
#3
EGR
 
grandamman

grandamman

G-Body Guru
Nov 7, 2005
607
121
43
up in the hills
#4
Didn't they have a problem with the torque converter not unlocking?
I'd check the fuel pressure and change the filter on the fuel side. How old is the gas?
Yes, the torque lock up may be the issue.
Try unplugging the connector on the trans.
You can reach it from under the hood.
 
W

Wageslave

G-Body Guru
Jan 25, 2017
733
483
63
#5
It could be a failing O2 sensor. I have seen them get lazy (slow response) and they would have problems with surging under load. If nothing else, they are cheap and should be changed when they get a lot of miles on them.
 
Huen79H/O

Huen79H/O

Not-quite-so-new-guy
Jun 5, 2018
39
88
18
#6
If it doesn't have mass air flow sensor then it should have a map sensor check vacuum lines to it and watch the voltage when driving
 
1evilregal

1evilregal

Royal Smart Person
Apr 23, 2009
2,201
1,071
113
Greensboro, NC
#7
years ago, I had a citation that went all out of whack, and hard starting issues after the engine was warm.... turned out to be an e.c.t. telling the computer it was stone cold, causing a no/hard start issue with intermittent flooding... The general, it seemed, had many issues with the early 80's F.I. cars, and had completely redesigned the sensor and wiring, but it fixed the problem... your symptoms and system may differ, so results may vary...
 
O

oldsmobile joe

G-Body Guru
Nov 12, 2015
830
522
93
mpls
#9
sounds like the computer is thinking the old iac is still in place. i would clean the throttle body bores where the throttle blades are. just open the throttle and carefully run a shop rag or towel (no chemicals, brushes or heavy scrubbing) in the bore to remove any built up carbon. then i would disconnect to battery to clear any learned memory from the computer. then drive it to relearn its normal operating parameters.
 

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