After doing some maintenance on my 89 this winter. New plugs, wires, cap, rotor, injectors, fpr, radiator, thermostat. I now have a slight miss when warm that I did not have before. Kind of a jerky , erratic miss. Or perhaps the ECM is trying to adjust something. Totally drivable, but I just know it wasn't there before and want my smooth engine back.

Now have 2nd set of new wires and plugs. Seemed like an ignition miss. No change. Replaced injectors again with Bosch type 3. Cleaned EGR valve and IAC valve. Rest computer several times. No change

Good steady fuel pressure and solid 17 " of vaccum at idle. Propane makes no change. No codes stored.

I am going to replace O2 sensor this week and also have a guy put a data stream type scanner on to see what that shows. I am thinking that somewhere along the line by having the battery disconnected and reconnected I may have caused a voltage spike to the ECM.

Anyway, as there are considerable threads about this type of thing, but very few posts afterwards on what ACTUALLY solved the problem, I will update this when I know..

Thanks to all who have given me their guidance along the way. I must be livin right as I haven't gotten the smarta**S stuff yet!

Gary / Louisville

 

Hey Gary,I'm with you you on the smartass stuff.I'm now spending more time on punctuation and spell check than i am trying to pass information.
DISCLAIMER;Which to the best of my knowledge is true.
With the miss you describe it sounds more electrical than fuel related.Especially as you say you have replaced most of the fuel related components.I don't think it is O2 sensor related.Mine ran fine without one.I actually pulled most of the sensors on mine a few days back to try and help someone and the car ran fine or should I say it ran in open loop which is programmed into the ECM.In fact at WOT it reverts to open loop and ignores all the inputs.
Back to your problem.Mine was similar but at higher rpm.20,000 miles since I had changed anything so like you I went plug wires,cap,rotor and seven plugs.Still a problem.Anyway I had this expensive DYNA_MOD ignition module in there guaranteed to provide at least 25HP and I pulled it and put in a $29 NAPA unit and bingo.
Then I felt so bad I went back and spent at least an hour changing #8.
While you're in there spray it all out with some contact cleaner in case you have some tracking.
My advise may be bull**** but I hope it's well phrased,punctuated and spelt correctly.I am from the other side of the pond so you need to cut me a little slack here.
In case of confusion my spell check is set to the Oxford dictionary not Websters.

 

Check your injectors. It may be unrelated to the other work you have done, but a miss when warm is a classic sign of an '89's injectors failing (which they will all do - just a question of time). Put an ohm meter across the two terminals of each injector and see if they each read ~16 ohms. They should all be within 1 ohm of each other.

 

Hey Gary:

No smart azz answers from me as I do not like them either! You can throw parts at the problem with the hope of "getting lucky" and finding the problem. This costs you a lot of $$$ and time. However, you learn a lot about your car when doing this practice.

I strongly suggest you get a scan and see what is happening to the engine control system. The scan may not define the "root cause" of the problem, but it will tell you where to look.

Good luck on this,

Bob

 

Don't want this to come off as smart azz, cause it's not meant to be!

I don't know how many times I've heard (and been guilty myself) "I feel like and idiot". When we do work on our cars and end up with something like you've described guess what? It's time to go back and double...no triple check what we've just done! We've all sworn we have the plug wires on right.....just to confess guess what? or accidentally cracked the ceramic on a plug during installation! Last one I did was accidentally crimp the in cap coil wire causing a minor short.....felt like an idiot!

A scan is a good thing, and I scan mine.....but it won't always show things like this.

 

When I bought mine, it seemed to miss a bit, and pulled the plugs for a look-see. They were fouled black. All of them. Went to pick up a new set - parts handed me a set that didnt even look close. Long story short mine had plugs in it for a steel head (threaded halfway up shank then taper stop) . The correct ones had full thread all the way up the shank with a flat thread stop (the plug for the alumminum heads) . That was back in November, I cant remember the part #'s were but if you need 'em I can scrounge 'em up.
I hope thats not whats wrong with it but that happened to me.

 

Thanks for your input guys, will let you know what the scan shows up. As I said have replaced injectors again and that gave no change. 2nd set of plug wires and plugs. I am sure at this point that all the wires are attached to the plugs securely. Have spent a lot of time on wires and plugs. I do have to say that in total darkeness that I see a little wire glow from time to time. Saw this on both the new Bosch set and now a new set of Autozone just to try something. I was also seeing some light at a couple of the plugs also, like I was seeing light through the insulator part of the plug or the spark was leaking out of the boot. I checked plug tightness and even tried swaping a couple of plugs out. They are the correct plugs for aluminum heads. The wires are tight on the plugs. I have checked the new plugs for cracked insulators. This seems to move around from plug to plug. This is a very high energy system obviously and I am not sure that just because I am seeing some of this energy in total darkness, that this is what is causing the miss. I have asked the question if anybody else sees this and the answer has been no. With 2 sets of new wires and 2 sets of new plugs what the heck would be causing this? This is the only thing that I have seen that could be the problem and it doesn't seem to be visable until everything gets warm which is when the problem starts. Is the engine not grounded properly or something?

 

Same issues with my car. Done everything you have. I did pull and recheck my SP gaps and some were .027 thru .038 How did I do that? I figured I rushed the replace and mashed some closed and "who knows" goof the whole job struggling to find the holes. Took my time this time and didn't force any plug in and it does run better. BUT, not good enough. I too am getting a scan this weekend.

 

Don't worry about that glow you're seeing in the dark, I think its called the Aurora effect...or something like that. Its been discussed here many times. The important thing is you're not seeing any arcing in the dark.