92 LX rough idle and heavy exhaust fumes

lojo1

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Mar 10, 2022
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Okay, here I go again (on my own).....

I've recently (1.5 weeks ago) purchased this car, which my father owned up until 2019. The last owner put a cam (303 I think) in it and installed a Magnaflow exhaust (no catalytic convertors).
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My problem is it runs fine once it gets up to temp but until then it doesn't want to idle on its own and the exhaust fumes are nauseating. All my clothes smell like exhaust fumes after I get out if the car. If I immediately take it out to drive it runs fine but bucks at lows speeds. Out on the main road it runs great. I'm pretty sure I need to get it tuned. the car only has 82k miles and was definitely never a daily driver for the last 3 years. I post a video below of the cold start and what happens.

The last owner told me I need to just adjust the TPS. I checked it but having a hard time getting a good read from this low budget multimeter. It only has 1 decimal point and even with tiny pin connectors it reads all over the place. Where's the best place to put the black probe for grounding? Some say on the black TPS wire and others say ground it somewhere in the engine bay. And I assume I should get a better grade multimeter.
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Things I know about the car and what's been done:
Last owner installed a cam. He did say he has never changed the plugs or wires since installing the cam. And he didn't specify what cam he installed. I'm still waiting for him to respond. I removed and cleaned the MAF. It idled better when I disconnected the MAF while it was running. When I hooked it back up after cleaning it still would not idle properly. I have not done anything else to the car under the hood.

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I've done lots of research over the past few days but figured I'd ask the community some questions before I take it my mechanic because he's been overwhelmingly busy the last few weeks. Thanks for any advice in advance.

Cold start video is below - PS: The belt squeal was fixed with some CRC Belt Conditioner.
 

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General karthief

wonder how much it would cost to ship you a pair
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You did not 'fix' the belt with the CRC, band aid. Take the belt off and spin the pulleys, they should not make any noise, look at the tensioner, with the belt loaded, there is a indicator with a pointer that shows how tight the belt is, I'm gonna guess you need a new belt or tensioner.
Now to help you out with some things:
First, the low rpm bucking problem is likely the cam, not much you gonna do about that right now without knowing what cam is in it.
Second, to check out how things are working, do the 'surging idle checklist', here's a link:
Read through it, then do the steps one by one, if you have any questions post them in this thread so we can help you out.
Don't start randomly replacing or upgrading stuff, it makes diagnosing problems harder.
Also most mechanical shops don't know how or can confuse the diagnostic stuff with our computer systems, they are used to working on newer systems so unless they work with what is basically the first generation computer systems you may be wasting you money,
 
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Monkeybutt2000

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Firstly,you do not need a "tune". Secondly,you need to pull codes. Follow the Generals advice above. And thirdly,a cam on a stock engine is just a disaster. And,that open air filter isn't doing you any favors either.
 
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lojo1

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Mar 10, 2022
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You did not 'fix' the belt with the CRC, band aid. Take the belt off and spin the pulleys, they should not make any noise, look at the tensioner, with the belt loaded, there is a indicator with a pointer that shows how tight the belt is, I'm gonna guess you need a new belt or tensioner.
Now to help you out with some things:
First, the low rpm bucking problem is likely the cam, not much you gonna do about that right now without knowing what cam is in it.
Second, to check out how things are working, do the 'surging idle checklist', here's a link:
Read through it, then do the steps one by one, if you have any questions post them in this thread so we can help you out.
Don't start randomly replacing or upgrading stuff, it makes diagnosing problems harder.
Also most mechanical shops don't know how or can confuse the diagnostic stuff with our computer systems, they are used to working on newer systems so unless they work with what is basically the first generation computer systems you may be wasting you money,
Thank you very much. And you are correct. A band aid was only applied to the squealing belt noise. On another note I decided to check the plug wires and plug and noticed they were in bad need of replacement. I wasn't able to get any of the plugs out yet because I don't have the extended socket size to remove the plugs. I'll purchase that particular size tomorrow and check to see how the plugs are.

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lojo1

Member
Mar 10, 2022
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Charlotte, NC
Okay I found a socket for the plugs and removed the plugs for #1 and #2 cylinders. I'm thinking it might be a good idea to replace the wires and plugs before I go any further in the process?

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nickyb

WAIT,you now have a pair?
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Check/replace the cap n rotor while your at it.
 
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KRUISR

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If just needing to reset the idle I found like thread easier to follow than the Surging Idle Checklist. The info in the Base Idle Reset thread all came from the Surging Idle Checklist so you already have it all in link above.


Post #9 is what you want to read.

Resetting the idle correctly will obviously help cold start and should improve the bucking you are currently experiencing. Agree with others, that filter is not helping (put a stock box back on). You shouldn't NEED a tune with just the cam change as I see you still have the stock MAF (I assume then the stock injectors are still there too).
 
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lojo1

Member
Mar 10, 2022
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Charlotte, NC
Okay I changed the plugs, cleaned the IAC and MAF. Car actually runs much better after cold start but had to be restarted a few times before it would run without giving it some gas. There was no bucking once I got on the road at low speeds. I'm posting some pics of the plugs I took out and the condition of the IAC once it was removed. Obviously the buildup in the IAC was pretty bad. Ran a code check after driving around and got codes 11,10 then 66 (MAF low voltage error) and 96 (Fuel pump error). I did notice the car idled better when I unplugged the MAF.
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Added a little video of the car after the small changes.
 

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vristang

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Sounds like you made good progress already!

Parts mismatch is always a concern when you don't know the complete history...
What ecu do you have? What MAF housing/sensor (looks like stock 55mm housing, sensor part numbers)? What injectors? Is there a chip installed in the ecu?
 
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