Surging/Hesitation
heavyredchevy
12-02-2006, 03:03 AM
Im having a problem with my truck where im having a bad idle (surging/missing) and what is almost like a flat spot/hesitation in the throttle at times. Sometimes it even just shuts off completly at a stop. I have replaced a lot of the sensors in the past except for the knock, ECT, CKP. The EGR valve, and EGR solenoid has been replaced along with fuel injectors, and fuel filter. Could this be a pickup coil problem, or an igniton coil? I dont think its a fuel pump problem, this has been doing this for a long time now, and is very random.
Thanks
Thanks
randy78
12-02-2006, 12:15 PM
have you removed and cleaned the IAC in the tbi unit yet, have the TPS tested or find the instructions online or from a technician on how to test it with a multimeter
good luck
make sure the fuel pressure is normal and that the O2 sensor is ok, as they dont last forever either
the flat spot in the throttle sounds like fuel delivery or TPS issue, the TPs is one of the sensors involved with fuel delivery, so...
good luck
good luck
make sure the fuel pressure is normal and that the O2 sensor is ok, as they dont last forever either
the flat spot in the throttle sounds like fuel delivery or TPS issue, the TPs is one of the sensors involved with fuel delivery, so...
good luck
2000CAYukon
12-02-2006, 12:53 PM
heavyredchevy,
I recently fixed a miss problem on my 90 GMC K1500. I also have a surging idle that I have not fixed yet but it is not as bad as before I fixed the miss.
In my case, the vents on the base of the dist were clogged and the terminals where the pickup coil connects to the ignition module were corroded causing a bad signal from the pickup coil.
I cleaned the vents, sanded the pickup coil terminals on the ignition module and coated them with dielectric grease. My low end miss was finally gone. Note that the ECM needs to relearn the fuel trims and it may take a week or so to relearn.
The pickup coil and magnet on the pole create an ac (alternating current) signal. This signal is converted to a dc signal which is used to fire the coil. It is also used by the ECM to fire the injectors.
If the pickup coil is weak or if there is a bad connection to the ignition module, a miss can occur.
In my case, when I disconnected the EST connector and watched the timing, it would jump around. This was caused by the bad connection at the ignition module.
//2000CAYukon
I recently fixed a miss problem on my 90 GMC K1500. I also have a surging idle that I have not fixed yet but it is not as bad as before I fixed the miss.
In my case, the vents on the base of the dist were clogged and the terminals where the pickup coil connects to the ignition module were corroded causing a bad signal from the pickup coil.
I cleaned the vents, sanded the pickup coil terminals on the ignition module and coated them with dielectric grease. My low end miss was finally gone. Note that the ECM needs to relearn the fuel trims and it may take a week or so to relearn.
The pickup coil and magnet on the pole create an ac (alternating current) signal. This signal is converted to a dc signal which is used to fire the coil. It is also used by the ECM to fire the injectors.
If the pickup coil is weak or if there is a bad connection to the ignition module, a miss can occur.
In my case, when I disconnected the EST connector and watched the timing, it would jump around. This was caused by the bad connection at the ignition module.
//2000CAYukon
heavyredchevy
12-02-2006, 05:36 PM
The IAC is new and set to specs, The TPS is new and also set to specs. I had the TBI off and cleaned all out. I replaced the injectors because they were dripping. Like i said i dont think its the fuel pump, i checked the pressure before and it was within specs. The fuel filter and line are new. The old on was falling apart. This is why i think it has something to do with the ignition. I really think its my pickup coil or something to that effect. I will check the things you said 2000CAYukon. Its below 0 outside right now and i dont have a garage to work in so ill have to wait untill i can bring it into the shop at school. Wyotech has a great program. They teach mostly theory so i need to get some experience for myself.
heavyredchevy
12-04-2006, 07:48 PM
Today I was at a red light and the thing just cut out on me completly. It took a few minutes of cranking to get it started again. This is starting to become a real problem for me. Could this be the pickup or ignition coil? How can i test for problems.
Tall
12-04-2006, 08:02 PM
Its a good chance it the pick up coil. Sounds like a problem a friend of mine had. Is it missing through out the RPM ranger?
Well; take the cap off; and look at the coil. Is it flakey? or Green looking? If so you should replace it.
Also test to see if the distributor shaft is wobly by turning the rotor and see if it wobbles at all.
Well; take the cap off; and look at the coil. Is it flakey? or Green looking? If so you should replace it.
Also test to see if the distributor shaft is wobly by turning the rotor and see if it wobbles at all.
2000CAYukon
12-04-2006, 09:03 PM
Its a good chance it the pick up coil. Sounds like a problem a friend of mine had. Is it missing through out the RPM ranger?
Well; take the cap off; and look at the coil. Is it flakey? or Green looking? If so you should replace it.
Also test to see if the distributor shaft is wobly by turning the rotor and see if it wobbles at all.
On my 90, I could not see the pickup coil by taking off the cap. It has an RFI shield over it. In order to replace it, you need to pull the shaft out.
In my case, the plastic housing around the pickup coil had cracked and it looked very rusty.
If you have any play in the upper bushing, you will be better off replacing the dist since it will come with a new pickup coil, shaft and ignition module.
//2000CAYukon
Well; take the cap off; and look at the coil. Is it flakey? or Green looking? If so you should replace it.
Also test to see if the distributor shaft is wobly by turning the rotor and see if it wobbles at all.
On my 90, I could not see the pickup coil by taking off the cap. It has an RFI shield over it. In order to replace it, you need to pull the shaft out.
In my case, the plastic housing around the pickup coil had cracked and it looked very rusty.
If you have any play in the upper bushing, you will be better off replacing the dist since it will come with a new pickup coil, shaft and ignition module.
//2000CAYukon
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