Wicked miss

[Ratrace427]

I have been working on this car. It is not my car so i do not know the full history. The injectors, plugs, wires, and fuel dist. have been changed. I can see this with my own eyes. I also saw that the three idle control bolts were screwed out and the idle mix plug had been drilled. After running the the three adjustments back in it was running rich. I leaned it out through the drilled hole just by finding a happy medium which was almost one half turn out. It is running much better with the new injectors and the mix adjusted but it still has a very bad miss under a load. When you give it gas really fast you can hear the flutter. You also have to down shift when going up a hill because of the very bad shake you get from the engine. I am thinking it is a compression problem but first i would like to ask if anyone knows the original position for the mix bolt? For example can i turn it all the way in till it stops then turn it so many turns out? Running rich or lean should not make a miss so i am still kinda curious what is making the miss. I think i will take all the plugs out to look at each one. I only took a few out and they were out of the box new so i didnt take them all out.

thanks for any input

[Ratrace427]

I just brought the car over to a friends house about 15 min away. The cat. is glowing red from the unburnt fuel. One of the cylinders must not be firing. I am going to pull every plug and see what i find first chance. Looks like the car is sitting for a few days. Now the question is why it is not firing with new plugs and wires. Unless someone changed some of the plugs and not all. OMG! i think i just figured it. Someone opened the idle control bolts after the new plugs were put in. It was driven like that for to long and one of the plugs has melted from the lean condition. Thats my newest theory that i just came up with.

[Ratrace427]

I was regretting the drive at first but tonight was the first time out in the dark. When i got it home i found that the muffler was also glowing red. No wonder the heat shield is burn out by the crank pulley. This thing has been messed up a long time.I also found out that the headlights are pointed down at the ground. So no regrets driving it with its conditions because i found new problems to fix. yay...

[sdg3205]

Run the injectors in a bottle and verify spray pattern. There are instructions available here with a search.

You can also reset your mixture baseline here, which might be wise.

Use a timing light to verify each plug lead is functioning properly.

Pull and inspect all plugs.

[Bitsyncmaster]

You do not set the mixture for best idle. If you do set it that way you will have adjusted it rich and moved the mixture so far off it went open loop on the lambda system. Now you're starting conditions are all way off.

Do the base line setup or get a dwell meter to adjust the mixture properly.

[sdg3205]

What Dave said. The sealed/plugged mixture control hex screw is what it sounds like... for mixture adjustments and is VERY temperamental; tiny adjustments go a long way. If your mixture is too far off in one direction or the other even a dwell meter wont help because the FV (frequency valve) wont respond. You need to pull the injectors, place EACH in a clear bottle, jump the fuel pump from the relay (brown to white/purple IIRC - i'm color blind!) and verify good spray then back off the mixture screw until the injectors just close... look for drips or injectors that refuse to close. Likewise, when you're verifying spray look for injectors that refuse to open. You can use the pressure plate to run your test. Total fuel dumps should be fairly consistent between all 6 bottles.

The top screw you'll see hits a switch. It's the idle speed micro switch screw, which the bottom screw is the curb idle screw and has the most impact on actual idle RPM.

Those two screws need to be adjusted so the car idles around 775 rpm, with the top screw engaging the switch to facilitate the idle.

Also, what's your name? It would be nice to address you properly!

[DeLorean03]

In May 2013, I developed a very nasty miss, and it was completely out of the blue - no prior symptoms or indications it was going to happen at all. Turned out to be a bad cap and rotor. Just food for thought.

I'd get myself a digital ignition timing light so I could see the RPMs and attach the timing light to each plug wire one at a time until I found which one had RPMs not like the other. From there, check that fuel injector to make sure it's spraying properly. If spraying fine, I'd ground that plug to the engine to verify strong blue spark. If no spark, swap plugs to see what happens - if good spark when swapped = just get a new set of plugs, if not = head underneath the intake to diagnose the integrity of your plug wires. If the plug wires test good by means of a digital multimeter (test for resistance), then it's a bad cap/rotor - if not - you'll read very high resistance or your multimeter will say something like "OL" - meaning the plug wires are broken = need new plug wire(s).

Hope you get it; I know how much it sucks to have a engine miss. I hate that crap.

[Ratrace427]

My name is J.T. I was a very active member back around 06 but havent had any issues with my car to talk about. I found the miss just now on my lunch break. #2 plug fouled. Gas fouled due to the mixture being f'ed with, bad injectors, and the three idle adjustment screws turned out. Poor thing =( I am glad it was on the easy side. The driver side plugs are really tight. I could feel my 3/8 extension twisting, so i stopped while i was winning. After work i will let it warm up to adjust the mix screw if need be. It smells a little rich now but i didnt let it warm up past the cold start injector.

[Ratrace427]

I just took it out to do the headlight adjustment and now i am upset because it runs better than my car. Why should it not? Everything is new now. I can hear the dwell..It goes buzz about 75% of the time where my car buzzes all the time. Maybe i need to drill a hole to adjust the mix. 75% buzzing good? I think i read that somewhere. Anyways it takes fuel better than my car but i am running %10 where i put %100 91 in the other.

[Ratrace427]

The proper term would be frequency valve now that i am thinking about it. But yeah its buzzing about 75% of the time where as my car buzzes all the time.

[Bitsyncmaster]

The frequency valve (FV) should always buzz when the engine is running. You may not hear it depending on what duty cycle it's running at. The grade of gas has very little effect on the FV.

[Ratrace427]

I didnt think the FV was effected by the quality of fuel that i use in my car but i have been using the cheapest for so long i really couldnt remember. I guess i will leave it alone with the mix screw where it is at. It runs very good but i am concerned about this winter and the mix leaning out to a unsafe condition. If i was the one driving it i would listen for detonation but a older man with older hearing owns the car.