I have had a bumpy idle ever since I redid the top of the motor this past summer and havent figured it out. The IAC system is working fine and the EGR is ok. im pretty sure all the sensors are good (CTS,IAT,MAF) because I replaced them all.

I hear a ticking when I first start the car in the morning but it becomes less noticable after awhile. I originally thought that my valves were out of adjustment and have since lashed them twice after the rebuild. I am looking for all the possible options as to what the HE** this could be.

Thanks for any help.

 

it could be an exhaust leak. Check the manifold gaskets (or header gaskets). It also might be a bad lifter but it would be more of a light knock than a tick.

 

Nope -- definately not an exhaust leak. I checked that only last week.

 

88,

Even though you feel comfortable with the rework you have done, it's time to step back and take a fresh approach to the engine. Verify your work with a compression test. If all cylinders are even and at good pressure, you can presume the valves, head gaskets, and rings are all sealing. If not, you may have a better handle on the problem. Once you have established a good compression reading on all cylinders, check the ignition system throroughly. Marginal wires, cap, rotor, or spark plugs aren't going to make the diagnosis any easier. If the ignition is in good condition and the timing is correct, consider the possibility of a valve that is not operating correctly. A cracked spring, bent push rod, pulled rocker stud, deformed rocker arm, or leaky lifter can ruin the valve action, effectively killing a cylinder but providing a good compression test. If you get that far and determine that all the components are intact, you may want to use a dial indicator to measure the lift of each cam lobe. A lobe that is worn nearly flat will operate a valve enough to provide a good compression test, but will also kill a cylinder in normal operation. A worn lobe should also be apparent in manifold vacuum reading as a "bounce" in the needle at idle, but maybe not always.

If the ignition, compression, and valve train are correct, the last part of the equation is fuel delivery. You can performa a power balance test on a TPI engine pretty easily to determine if you have an injector problem.

To perform the test, start the engine, allow it to reach operating temperature, then unplug the IAC electrical connector while the engine is idling. Unplug the electrical connector from one injector and monitor the engine RPM as it is disconnected. The drop in idle RPM and change in idle quality should be relatively equal through the firing order. Replace the electrical connector and go on to the next injector. You should realize that the ECM will sense the RPM drop and attempt to compensate by adjusting the IAC, which is why it was disconnected in the first place.

Compare the RPM drop at each cylinder. When finished, don't forget to replace the IAC connector. If one or more injectors caused little or no change in RPM, it is not flowing fuel at the correct rate.

NOTE: This test will not be accurate if the ignition system is not in good order or compression is low on a cylinder.

This test allowed me to identify two defective injectors, and test results after removal of the injectors confirmed that - two of them had very poor spray patterns and low flow rates. The engine had 18,000 miles and I had already tried several types of injector cleaner in the fuel tank with no improvement.

One of these steps should get you closer to a solution. We'll be watching for the results.

 

Vader-- as always you are a bastion of good info.
:hail:

systems I can verify by the tests you mentioned are:

1. Compression is even across all cylinders (tested last week)

2. Ignition is functioning properly (replaced C&R and wires and did a pull wire test like the injector method you described to see if all cylinders had spark) timing is at 8BTDC with stock chip (also verified)

3. spark plugs are all tan

4. fuel pressure test came in rock steady at 45psi idle and 38-43 with vac attached all the way to redline but not under load.

I will do the injector test you mentioned and recheck my ignition stuff b/c you never know what napa will give you.

I cant really check any cam clearances right now as this is my daily driver but I will be doing a cam swap soon (3 months) and well see what that turns up.

Thanks