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'88 s10 won't, then will start and dies when driving
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tim74
New User
Nov 23, 2006, 10:24 PM
Post #1 of 4
(4513 views)
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'88 s10 won't, then will start and dies when driving
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So my brother is going mad trying to get a 88 s10, 2.5, manual, throttle body injection to run correctly. He's been through the fuel system, new pump, been through the distributor and gets a constant error code related to the throttle position sensor. He said he replaced it but it still comes back.
The vehicle needs to be cranked incessantly and eventually will start and idle high but roughly as you can detect a miss. Then it settles down and idles smooth a bit fluctuates, then dies. When you try to drive it, it chokes out and dies. He showed me the problem tonight and it took about 10 minutes to start. Fuel was dropping onto the throttle plate. I pulled a plug and it was thowing spark and that's about the time it started up.
So we have fuel, we have spark. He says the distributer and top dead center are matched up correctly but the under hood procedure says something about turning the timing an additional 8 degrees which he has someone lined up to do among other things. I wouldn't think it wouldn't start because of a minor timing problem. It should start. I asked him if he's sure the camshaft is turning(you never know, I figured it wouldn't start if the valves were stuck open) and he said yes and I'm sure that's true since it will start eventually but not stay running.
So I guess the fuel system has been worked over, a new distributor, plugs, wires, a few sensors and the throttle body was rebuilt. I also noticed a fresh oxygen sensor.
I suppose the timing chain could've jumped but I haven't had much experience with these gremlin type problems or with timing.
Any answers are greatly appreciated.
(This post was edited by tim74 on Dec 3, 2006, 10:36 PM)
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tim74
New User
Nov 26, 2006, 12:28 AM
Post #2 of 4
(4493 views)
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Re: CURED!! '88 s10 won't, then will start and dies when driving
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After talking to a friend and looking over the EGR symptoms, it seemed like some of the symptoms of an EGR problem partially matched his problem. By the time I got to my brother's he had already been through the EGR and the vehicle (when it finally started) choked out after depressing the EGR diaphragm as it should have. We then futzed with the sensor for the EGR and bypassed it. No change. Then my brother noticed the junk car the landlord had in the driveway have the same engine and throttle body. I tested it's vacuum, it seemed fine. Then he told me it would start on stuff like brake cleaner. I grabbed some from my car and sure enough, it fired right up with some brake cleaner sprayed in there but would die out as always on the fuel after several idle surges or by depressing the gas pedal even moderately.
He decided to grab the throttle body from the junk car and see what happened. He swapped the injector and really no change, then he decided to change the whole unit. Well, his throttle position sensor code went away but the vehicle ran the same. I inspected what I could when the tbi was off and began to wonder what the sensor on the intake manifold was in the corner.
We almost gave up for the evening. He pulled the sensor and it looked similar to a mass airflow sensor. I later learned it's actually an air charge temperature sensor. The one on the junk car didn't look much better but I sprayed some brake cleaner on it and it cleared up some. We made sure it was dry and installed it. The vehicle cranked some, I don't remember if I helped it start with brake cleaner but it fired up eventually. Then he began revving the engine, something he has never been able to do since owning it and it was obvious that was the problem. The engine idled smooth, no more popping. It settles down without choking itself off and we took it out for a test drive which was perfectly successful.
He's still letting it soak in, he's pretty ticked he's gone through $300 when it was a silly sensor he could've gotten for free in his own yard. Air Charge Temperature Sensor-I didn't even know what one was until today. It makes sense now, it reads low and keeps dumping fuel resulting in it flooding out. That's the only reason it kept dying.
I hope nothing changes tomorrow and it starts successfully when cold.
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tim74
New User
Dec 3, 2006, 10:50 PM
Post #3 of 4
(4475 views)
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Re: '88 s10 won't, then will start and dies when driving
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Of course I spoke too soon about a cure. He had some problems the next day. Still doesn't want to start without considerable cranking. Will run now with spirited throttle play but will not hold an idle even though that control is brand new as well. There is no dead spot in the acceleration and the truck will go down the road now. It just won't start correctly and won't idle right.
It appears to me it is simply a flooding issue but the cause is perplexing. I have no other vehicle to compare it to and see how much fuel that injector drops normally. The vehicle fires right up if we spray brake cleaner in the throttle body. Once it's run some, it'll restart easier without help as it should. I see the fuel and spark, my theory is that there is too much fuel to atomize correctly. When it is running, and the throttle plate is opening up, the barrel is awash with fuel. With all the sensors being new and the injector being swapped out, the only thing left to wonder is the computer's pulse control on the injector though I do wonder about cylinder compression too. If the compression is bad could the fuel just not matter until it's warmed some from cranking but has no choice but to fire with something easily flammable such as brake cleaner?
Is this a common problem for a bad computer control to have as far as dumping too much fuel from the injector?
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steve01832
Veteran
Dec 4, 2006, 3:43 AM
Post #4 of 4
(4474 views)
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Re: '88 s10 won't, then will start and dies when driving
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Just for kicks, check the EGR Valve to make sure it is fully seated closed. Watch it as the engine is started. If the pintle starts to open, replace it. Also, replace the EGR solenoid if engine is equipped with one. It's been a long time since I've worked on an 88 and I don't have a wiring diagram at home for it.
P.S. With the engine running in neutral, slowly open the throttle while watching the EGR. It should not open at all.
Steve
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