Help me diagnose a problem

[E30Nova]

Well, I disconnected the supposedly "good" AFM and the idle smoothed out. Put on the one that was messed with and it stayed smooth. Put the "good" one back on and it's still smooth but every now and then it starts shaking.

Anyway, I didn't remember if I hooked up the hose for the charcoal canister so I decided to check that out. Unfortunately I did hook it up, so that wasn't my problem, BUT, I figured while I was there, I'd check that connection that nando was talking about. Sure enough, when I unscrewed it, there was a little green forest growing inside.

After cleaning that up, I don't have the WOT problem anymore. :-D:-D:-D

Only thing is, like I said in an earlier post, when I come to a light, my idle stays around 1500-ish for a few seconds and then drops to 900-ish. I don't remember it doing that before I swapped throttle bodies, so I'm going to see if the throttle is closing enough at idle. Otherwise, anyone have any ideas as to why it's doing that?

Matt

[E30Nova]

Bump.

Matt

[E30Nova]

Well, I bought a new pulse sensor. It measures 560 ohms compared to my old one's 33-ish ohms. Got that installed and it didn't change a damn thing. So I grabbed my phone and took a video of the idle.



Look how bad the engine is shaking. :(

And then at the end, I show my clean hand, put it behind the tailpipe and after a couple seconds it's covered in black stuff.



Matt

[E30Nova]

Your TPS won't click at the WOT end of the travel, only at the idle end so that should not be an issue.

Interesting. I could have sworn the Bentley said it was supposed to click and/or change resistance at WOT. I don't get either one of those, which is why I changed the TB in the first place.

Still, I checked the resistance of the pulse sensor just on a hunch and it only has like 33 ohms. I could swear I replaced it shortly after I bought the car, but I'm not 100% sure. The car idles rough as hell and the car shakes like my Nova with a big cam and solid motor mounts. I figure the pulse sensor has to be bad just because the Bentley says it should read around 540 ohms, but before I buy a new one I'd ask you guys.

Would a bad pulse sensor create a rough idle? I thought it would either be perfect or it wouldn't even start, but I dunno.

Matt

[RoDo]

One thing I remember is that the "good" throttle body I got didn't click when I went to WOT. No matter how I adjusted it, it would click off idle but not at WOT. Tomorrow or Saturday I'll try driving the car with the TPS disconnected and see if it makes a difference.

Matt

Your TPS won't click at the WOT end of the travel, only at the idle end so that should not be an issue.

[E30Nova]

One thing I remember is that the "good" throttle body I got didn't click when I went to WOT. No matter how I adjusted it, it would click off idle but not at WOT. Tomorrow or Saturday I'll try driving the car with the TPS disconnected and see if it makes a difference.

Matt

[36brua]

well lately my car is doing the samething after it (the car) gets hot will not pull but will idle, let it cool and it runs like a bat outta h---. gets hot and like tonite called a buddy with a wrecker, will check in the next couple of days but my bet is fuel pressure issue (fuel pump). Since I can go outside right now and drive to the store and back without incident. any takers on a bet?

\

may sound strange but have you tried a different set of plug wires/pickup ?
I had a similar 'hot' running prob.would not take throttle. replaced wires fixed... after replacing some , checking rechecking all the usual suspects .. always something new good luck

[e30evt]

well lately my car is doing the samething after it (the car) gets hot will not pull but will idle, let it cool and it runs like a bat outta h---. gets hot and like tonite called a buddy with a wrecker, will check in the next couple of days but my bet is fuel pressure issue (fuel pump). Since I can go outside right now and drive to the store and back without incident. any takers on a bet?

[E30Nova]

Yeah, so I drove the car to work last week and it's still doing the stupid WOT thing.

I'm about ready to roll this car off a cliff. :-x

Matt

[E30Nova]

Well I put the new throttle body on and along with the new afm it seems like the problem is gone. The only problem is now it idles at around 1300 rpms. I'm 99% positive I don't have any vacuum leaks but there has to be one somewhere. :hitler:

Matt

[nando]

so when you disconnected the TPS the hiccups went away?

5ml difference could just mean you have a dirty fuel filter. fuel pressure is 42.5psi so a 10psi gauge isn't going to tell you anything. I'd look for a pressure gauge from summit racing or harbor freight.

swap that TB and see what happens

[E30Nova]

Well, I finally decided to get off my ass and try to diagnose the problem. I just bought an afm and throttle body last night. I haven't put the throttle body on yet because I'm too lazy to drain coolant, but I put the new afm in. I did the fuel pump test, though. Jumped the fuel pump relay for 30 seconds and only had 870ml, so I didn't even get the bare minimum according to the Bentley. I'll probably do the test again just to be sure, I mean is 5ml really going to make a massive difference?

I tried to do a fuel pressure test but I used a vacuum/fuel pump combo gauge that only went to like 10 psi, so it didn't really tell me much. Where are you guys getting fuel pressure gauges that work with M20's? I called Autozone and Kragen and they only had the kind with a screw on fitting.

Matt

[E30stan]

i had similar symptoms with my car, i was so sure that it wasnt a vacuum leak until i went to change my tps and noticed that small rubber tube under the throttle body had a tear in it right under the clamp, so sometimes it would allow extra air in causing the slam-on-brakes feeling, eventually it was fixed but then the o2 sensor went bad before i fixed it in time

[E30Nova]

Well I disconnected the TPS and tested it. Tested fine. Problem is, I broke the stupid fitting on the throttle body that has a hose going to the brake booster. I tried to JB weld it but you can hear it sucking. I put my finger around it and the sucking noise got quieter. I might try slabbing some more JB weld on it, but if that doesn't work, I might have to buy a new throttle body.

I also changed the SI board with a known working one (my batteries were at 2v and the one I put in had 3v) to fix my gauges. Now my idle is at 1500, and I'm pretty sure it's because of the vacuum leak since I used my original coding plug on the SI board.

Is there another way to fix those fittings? I remember reading somewhere that there was a "kit" to put new fittings in from the dealer.

Matt

[nando]

okay, what I was asking about specifically was coolant leaks. the TB heater has a cork gasket that will start to leak as it ages (or if the hoses are old, it will leak out of there).

a vac leak isn't going to cause the issue at hand. :p

don't think grease or oil really would anyway.

Actually, there is one test you can do that's pretty easy. disconnect the TPS and drive the car around for a while. When I had the issue of a wet harness, this solved the problem well enough for me to drive the car until I fixed it. if it stops cutting out then it's a wet harness. if it still does it it's probably something else. you'll be running on the cruise maps all the time though so it won't idle nicely and it will be slow..