Greetings all....I have a 1987 Delta 88 with a problem I cannot diagnose. No codes come up on the computer scan. Between 45 and 55 miles per hour, the motor will jerk real hard, like the transmission is shifting hard. Had the tranny checked and there are no issues. Anybody have any info.....Many thanks

 

Engine, transmission, and miles might help, and does it happen everyday?

 

Almost sounds like the transmission clutch lockup solenoid enaging or disengaging. It can often feel like another gear in the tranny. How long has it been feeling sharp or hard?

 

My dodge does that same thing. lock up engages too soon and motor jerks shakes etc. I just bypassed the tps with a potentiometer but my dodge is an older mechanical diesel dunno. You might just need a tps sensor .

 

so you're saying you have the potentiometer hooked up to the TPS harness and have somehow attached the throttle to it so that it changes voltage with respect to throttle position?

 

I had a similar problem, and also did not have any codes set either. It turned out to be the lock up solenoid in the trans. Once I changed it out, the problem was solved.

 

But back to the original question...The first thing that comes to mind is the trans lock-up solenoid. I know mine engages around 40mph, with light throttle.

 

yes the tps sensor on my dodge was bypased so when it hits a certain point thats when the lock up hits. I have it set to 45 ish 50. Dunno if it can be done on newer cars my dodge is a 94. It's a common kit for first and second gen dodge cummins trucks with tps sensors offer through high perf diesel shops. It's not hooked up to the throttle at all some how it still down shifts. I know the dodge and this car are diffrent but when my tps sensor was bad thats what it did.

 

I'm going to disagree here. Yes, it's possible for the solenoid to go bad, but the jerking you describe has led to the replacement of more good solenoids than anything else. The real problem is that when the solenoid locks up, any misfire in the engine is felt as a jerking in the drivetrain (just like in a manual trans car). If there are no codes set, the most likely problem is ignition. I had exactly this problem on a similar vintage GM car, and the problem (and misfire that caused it) went away when I replaced the ignition coils and module. Note that a bad coil or ignition module won't set a code.

 

x2 with Joe

 

The coils have been tested and they are good.....I replaced the ignition module and the car started once and died. Now it will not start with the new module at all. Is there some trick to the installation? Many thanks for your reply

 

The coils have been tested and they are good.....I replaced the ignition module and the car started once and died. Now it will not start with the new module at all. Is there some trick to the installation? Many thanks for your reply

 

Did you use the insulating gel?
Could have a bad unit, too.

 

You mean the white heat-sink grease?

 

No I did not.....Can you tell me what to do?...Many thanks

 

If the HEI module came with white heat sink paste, remove the module, open the tiny package, squeeze out the paste onto the bottom of the module, spread it evenly on the whole bottom, then put it back together.

If it came with clear, slippery stuff, then throw the clear stuff out, go to Radio Shack, buy a tube of heat sink paste, and smear it on the bottom of the module as above.

- Eric

 

I did not get anything but the module.....I am on my way to Radio Shack....Thank you

 

It did not work......The car will not start

 

The heat paste will not make the car run - it will prevent the module from burning out and stranding you.

I'm sorry that I didn't understand that you thought that.

The car isn't running because of something you did when you changed the module.
You need to slowly go through everything you did, and recheck every step.

Likely problems include one or both wires from the sensor pinched under the module or the vacuum diaphragm mount and poorly connected or corroded wires.

You should verify that you have 12V at the hot wire into the distributor.

Finally, you may have a bad module out of the box.
I bought one last week - had the store test the old one, it failed, had them test the new one, it failed, too. As they only had one, I had to go to another store to get one.
You can bet that I had them test that one, too, before I bought it.

- Eric

 

Greetings-----I cannot get the car to start after installing a new module. I have tried three seperate units, they all could not be bad. I put the old on back in and the car starts right up. I am at a loss

 

Ahhhhh... A mystery!

Well, first, never say never. They all could be bad.

Did you have them tested at the auto parts store?

Second, at this perplexing point, it would be beneficial if we could see some photographs of your situation. When things are behaving this badly, it is often helpful to have "another set of eyes" to look at what you;re doing, as there may be something simple that you're just not seeing.

Third, you need to be sure that nothing is touching anything that it's not supposed to be touching, that all wires are intact, with no breaks in the insulation, and that the connectors in all plugs are clean, tight, and making good contact.

Don't discount the possibility that the problem could actually be with the pickup.

Once you've done all that, get those modules checked.

- Eric