New plugs and wires = won't idle... Hmm.

So I've got a 1990 Renix 4.0.

Just did the plugs and wires, NGK plugs and some "premium" napa wires as well as cleaned the airfilter.

Went to start it, and it started like normal and revved to 1000-1200 rpm.

As the idle began to settle down to normal, it starts missing and slowly the idle keeps dropping and keeps missing till it dies completely. This takes about 15-20 seconds. If you give it throttle before the idle starts to lower there is a bit of a hesitation before it revs up, but it revs like normal. If you wait till its starting to miss/hiccup it won't rev, just keep missing and in some cases just dies.

Hmm.

So I change the wires back to the old ones. No difference.

Went through the plugs one by one changing back to the old ones. No difference.

So I'm back to where I started from and still having this issue.

I've checked vac lines, and to see if I may have unplugged anything. It doesn't appear so.

Also the firing order is fine, I did everything one by one, and I also double checked it after the fact.

SOOOO....?

Any suggestions on where else to work? I'm pretty unfamiliar with the layout/setup of how the Renix shit works, I'm used to Vw/audi stuff.

Thanks.

Check around the air filter and DS of the engine, check the vacuum line to the MAP sensor on the firewall.

Oops, see below

This sounds like what mine did when the fuel pump gave out (but I hadn't worked on it recently)

Link is to that thread:


http://208.101.10.250/~naxjaor1/forum/showthread.php?t=978424&highlight=revs

Keep looking for a disconnected electrical connection or hose. Didn't you read the thread that no other plug will work other than a Champion? LOL

So the plot changes a bit. I finally noticed that my ballast resistor had disintegrated into nothing.

Went to the FLAPS and picked up a new one. Now it won't die, BUT its idling at 2500 rpms now. And maybe its just me, but it appears to still have a slight hesitation if you flip the throttle open quickly.

Checked my idle screw on the throttle butteryfly valve/linkage, that seems to be backed out most of the way with no more room to make adjustment.

Thoughts?

I also pulled my neg battery cable to see if the ECU needed to be reset or something. No difference.

If this motor got "tuned" with a bad ballast resistor, would the timing be different?

Thanks for the replies thus far.

Ballast resistor just cuts fuel pump voltage after it's started to make pump quieter. Most people just run a wire around it. It makes no difference to how it runs or gets tuned up. No timing change. Make sure the plug didn't come off the IAC (idle air control valve). These often need to be removed and seriously cleaned. And test it to see if it moves.

IAC is plugged in and the connections are good. I pulled it to see if it made a difference while unplugged, same with the TPS, neither made the idle drop. I'll pull it and see if it needs a cleaning.

Hope this works . I need to get home tonight.

Make sure the plug didn't come off the IAC (idle air control valve). These often need to be removed and seriously cleaned. And test it to see if it moves.

Click to expand...

winterbeater is right that was one thing that i had to clean after i put in my new motor and then i had to put in a new crank sensor but i dont think that could be it

Well, pulled the IAC, cleaned it, it had a little gunk in it. Put it back in and now it idles like its supposed to.

BUT.

Now it won't accelerate worth a damn. Coughs, sputters, and misfires. If i'm just sitting there if I can get it to rev above 3500-4000 it smooths out and revs right up. Tried driving it and its the same story, cept more pronounced underload and I was never able to get the revs high enough to see if it would smooth out.

Maybe TPS now? I have some tools with me, but its getting dark and this is starting to drive me nuts.

Funny how its been running great, then I decide to do some maintenance and all this crap starts to snowball.

GRR.

Any thoughts on this new problem?

Thanks again.

Well, have you put the new stuff back on? Plugs, wires, etc?

You should have a slight amount of pressure on the throttle plate with the adjusting screw, it shouldn't be backed out all of the way. It should just be starting to open.

You need to adjust the TPS after you get the IAC and adjusting screw worked out.

??? Carefully unplug and re-plug all in the vicinity to clear a grungy connection??? try to warm it up see if that helps???
same for CPS + wiring clear???
Good Luck!

Ok. I'll try not to vent too much here, but I will say its amazing how many people cut you off when thats the last thing you need to happen cause you're limping a jeep home that will barely run and takes about a full minute to get close to an acceptable speed....makes me want to stab people.

Anyhow.

So, here's where it sits:

I went out to it after writing that last message, tested the TPS, its good, its within .01% with the primitive gear I was able to measure with, it may be closer than that.

Started it up and the high idle is back. I revved it a few times and it didn't misfire. Turned it off, then back on, and its back to idling like normal but misses when you accelerate. So I drive it home.

On the way home it was beyond the most extreme use of the word "touchy"... too much gas (basically any) and it'd start to misfire. However, if I got the revs high enough I could get on it and it would accelerate like normal (we're talking 3500rpm and up) (I also didn't discover this till I was in my own neigborhood as I didn't want to risk aggravating things further too far from home)...

I've gone through the grounds, or the ones I can think of, the few on the pass side block are a little greasy, but solid.

TPS we'll call within spec, the middle pin was ground, the top pin was .8 volts, and the bottom pin was 4.9 (maybe I have that backwards, but those were the voltages I got outta the digital readout on my Powerprobe.

IAC might be working properly? The gunk I cleaned out of it was more like just a thin coat of black residue from oil/gas whatever you usually find on an intake tract.

So...now I'm thinking, maybe O2 sensor? Maybe fuel pump, but I'm not so sure about that because it does accelerate without too much issue if I get the revs high enough. Seems kind of weird the O2 sensor all of a sudden going bad though, I'm pretty sure its on the new side. Anyone happen to know if it has a generic o2 sensor map it'll run if i just unplug it to test out that theory?

Or shall I just stuff this POS full of TNT and fire at it with a roman candle?

Its beer time.

Thanks for the suggestions so far guys, it helps.

Oh, and to further clarify:

The new plugs/wires are in it after I went through a couple sets of each and found no difference.

Also this is a manual tranny, hence the voltages I refer to as "in spec" are of the .17% variety.

And yes, the throttle valve adjust screw is set up with a slight pressure on it, not all the way out.... I could have worded that better before.

Before you blow it to hell, please test the EGR system.

Do not know about renix, but on newer system the O2 is not in the picture until it goes to closed loop.

-suggest getting fuel pressure readings to narrow down some.

-Congrads on getting home safely. (Whew!)

Good Luck

sounds like what mine is doing also, ive checked the sensors, and ordered a 02 sensor, ill let you kno how that goes tomorrow. I got good fuel pressure, put a bit of sea foam in the gas, and it made little difference, im betting its my fuel injectors.

I unplugged the O2 sensor today, no difference. It seemed to run a bit better when it was cold, then once it warmed up same thing its been doing, acceleration includes misfires and sputtering till it gets to about 3000rpm then it pulls just like normal. I drove it to again today, just keeping the revs high and with the O2 unplugged. Drove the same as yesterday with the O2 plugged in.

Don't have access to a fuel pressure guage. But I'm not totally convinced it has to do with fuel pressure as it seems to pull just fine in the higher RPMS. I'll check the EGR stuff today.

had a similar problem with a 99 wrangler. It turned out to be a MAP sensor, I had to pay the stealership to tell me. They even bent a pushrod revving it undermisfire.

Not sure if your 0DB 1 motor has one, it would be on the throttle body.
Check to see, also as suggested check your egr.

Be careful with that thing while its misfiring, it can put it under fast.hasta

MAP can be tested! Certain barometric pressure = known resistance.