My 85 L98 is my daily driver and I drive it to and from work, about some 35-40 miles. Most is at highway speeds but because I live in Maui, there is some city traffic I have to deal with. My check engine light started coming on in the previous month. It would only come on usually after driving the car for some 30 min or so and at highway speeds, around 55-60 mph. It would sometimes come on going to work, but mostly when I drive home and Ive hit the highway. When it comes on and I stop the engine, like running into the store before I get home, the light will no longer come on. The car will idle fine, no erratic idle, and will start up fine. The only time it sounds like it might die is when I back down the hill of my driveway when I have the clutch in and steering the car into my spot. Now after replacing my intake manifold gaskets the check engine light will immediately come on when started in the morning and coming home, it won't come on at all.

My question is does the EGR code really mean the EGR valve needs replacing? At $80 I want to make sure its the valve before dropping that much money. Ive also read that the knock sensor could also set off a code 32. Is this true? The vacuum lines seem fine and I haven't gotten to test the circuit as in the Haynes Manual. And what do I look for or test for the code 42? Its the EST circuit and the only thing Ive touched from the gasket replacement was the whole distributor assembly and related connectors. A couple months ago I replaced the Ignition module with an Accel Ignition Module and I never got the light after doing that til now. Am I missing something here? Sorry for the long post but if I can just get some answer, I will be greatly appreciated. Thanks.

 

Couple of quick thoughts...

EGR code - try removing the vacuum line from the EGR valve and plugging it (plug the Hose). This way the valve should be shut and Stay shut - if the code still sets it's either because the EGR temp sender is faulty (the sensor is just looking for how hot the manifold is below the EGR valve seat - if it sees hot when it Shouldn't then the code sets) or because the valve really isn't shutting all the way and will need to be cleaned and/or replaced. If the code does NOT set with the valve disconnected, but does set with the valve hooked back up, the valve is still not likely the problem - the Control solenoid is a more common failure. That should be tested first..

ESC circuit. Could be the knock sensor, could be the ESC module (down by the evaporator core on the pass. side). Could be the ignition module (in the distributor cap), although that's probably the Least likely. Although - you say you recently replaced that ignition module - bad parts happen, and Accel stuff (in my experience) isn't the most reliable on the planet. Could also be the ECM, wiring or connectors, or.. you'll have to step through the service manual diagnostics to sort That one out properly. Get the Helms book and save yourself the aggravation of trying to use the Haynes wastepaper.

Does the car have any kind of rattles or knocking sounds, particularly when cold - valvetrain, piston slap, accessories, etc? If so the ESC circuit might not be actually Bad, might just be seeing those sounds as "knocking" and trying to tell you about it.

 

replace the egr temp switch, cost 18.00, start there

 

Is there anyway to test the Ignition Module to see if that is the culprit for the code 42 other than getting another Ign module and putting it in? How could I test the knock sensor and the ESC sensor? There is no knocking or any kind of that sort when running the engine so it can't be the knock sensor right? So do I clear the codes, plug the hose to the egr, then run the car to see if that sets off the code again?

 

Rarely. The code 32 indicates an out of parameter (bad) reading come in on the EGR circuit. It doesn't mean the EGR valve is bad, and usually it isn't. Get a hold of a FSM (Factory Service Manual) and follow the trouble shooting charts for each of your codes, to minimize replacing good parts.

RACE ON!!!

 

My "91" was setting the Service Engine Soon light just as you described and after going through the steps in the FSM for EGR diagnosis everything checked out fine but, the SES light continued to display.

I finally just replaced the EGR valve and the SES light went away.

 

Same for me

 

An intermittent code 32 sounds like the EGR temp. switch. Hardest part of replacing the switch is getting at the connector that's behind the distributor. Look and see if the porcelean around the wire is cracked. You can also test the EGR valve by applying some vacuum to the valve and see if it holds or leaks - much easier than pulling the plenum.

The code 42 EST circuit might be an unplugged EST wire (around Left rear valve cover). You unplug the EST wire only for setting the timing.