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Please notice the pop through the intake. It does this if you open the throttle too much. I believe this is a fuel starvation issue. I can get it up to about 1500 rpm max.
Engine is displaying no codes, spark is set to 6 btdc, checked for a vacuum leaks, fuel pressure is rock solid at 41 psi. I have one bad injector, so the engine is running on 7 injectors, but that should not cause this issue.
I think the computer isn't opening the injectors long enough.
It doesnt sound like it is getting any additional fuel, check the TPS voltage. All I hear is the throttle body opening. It sounds like it is still idling with just the butterflies opening.
I ohmed out the injectors, all tested 16.6-16.8, except cylinder #8... 3 ohms. So that one got unplugged.
Spark is good as far as I can tell.
Regulator seems to be good. Fuel pressure stays healthy throughout testing.
I have not checked any other sensors besides TPS. It gets 0.74v at idle and 4.2v WOT
Again, the ecm isn't giving me any indicators of an immediate issue.
When I got the car, the icm was suspect of not supplying a reference signal to the ecm. I wonder if the icm could still be an issue.
I think you need to visually see the injector pulse. I do not know if a meter with a duty cycle can measure the injector pulse. It would be a good time for a the ability to read live data.
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The injector pulse does not, in my opinion, seem to be changing, it is idling. The pulse width is not increasing with TPS voltage increases. That is a guess of course, but your car is idling.
Could I verify TPS response by watching the timing at I move the throttle?
I'm thinking if the timing stays put while changing the throttle, its not seeing TPS signal?
Again, I'm skeptical of the ICM. Does this effect anything other than injector timing?
I think the popping is the fuel / lean condition caused by throttle plates giving so much air without additional fuel. You can use a timing light as a basic spark tester on any cyclinder as long as you keep the sensor away from other wires. All I hear is an idling engine. If you give it full beans and it does not increase in rpm you would (I think) have a very rich smelly exhaust, do you ??
No, you can not verify injector pulse width with a timing light. Does your DVM meter have duty cycle ??
Anyone working on their own OBD1 car really needs to have live data. It makes figuring things out a lot simpller. Otherwise you just keep guessing. It well worth the investment-take a look at tunercat, their datacat software with cable. That and a FSM will be well worth it and save a lot of frustration.
I'll put my vacuum gauge on it next time I work on it.
Both sides of the exhaust blow out nice crisp puffs of exhaust... Could still be a restriction I suppose. The guy said he straight piped it, but there are cats and mufflers, so who knows what's going on under there
I'm going to give it a shot of something flammable next time while trying to open the throttle just to see how it reacts.
Does unplugging the MAF trigger the SES light? Because it does not on mine, nor does it seem to affect how it runs. Strange.
Too many things are pointing to the ECM.
Nearly everything I have tried indicates that the ECM is getting the proper inputs, but it cannot produce the proper outputs.
I have one ordered and will update if that fixes it.
Too many things are pointing to the ECM.
Nearly everything I have tried indicates that the ECM is getting the proper inputs, but it cannot produce the proper outputs.
I have one ordered and will update if that fixes it.
This is a great thread! Did you go with the ECM, the EPROM, or both?
06-28-2024, 08:20 AM
l98 Refuses to take throttle
