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92 LX rough idle and heavy exhaust fumes

  • Thread starter Thread starter lojo1
  • Start date Start date Mar 12, 2022
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    92 fox body mass air flow rough idle strong exhaust fumes tps

lojo1

Member
Mar 10, 2022
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Charlotte, NC
Mar 12, 2022
#1
  • Mar 12, 2022
  • #1
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).


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.

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.



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
20+ Year Stangneter
Aug 25, 2016
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Mar 12, 2022
#2
  • Mar 12, 2022
  • #2
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:

Help me create the "Surging Idle Checklist"

Updated 26-Oct-2019 to clarify creeping idle RPM increase as the car is being driven. Many of you are familiar with the "Cranks OK, but No Start Checklist for Fuel Injected Mustangs" checklist and the No Crank Checklist. They are very effective in finding and eliminating the problems by use of...
forums.stangnet.com
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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M

Monkeybutt2000

Mustang Master
Aug 11, 2019
1,387
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133
Lafayette,IN
Mar 12, 2022
#3
  • Mar 12, 2022
  • #3
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.
 
Reactions: JD1964 and lojo1

lojo1

Member
Mar 10, 2022
31
25
18
Charlotte, NC
Mar 12, 2022
#4
  • Mar 12, 2022
  • #4
General karthief said:
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:

Help me create the "Surging Idle Checklist"

Updated 26-Oct-2019 to clarify creeping idle RPM increase as the car is being driven. Many of you are familiar with the "Cranks OK, but No Start Checklist for Fuel Injected Mustangs" checklist and the No Crank Checklist. They are very effective in finding and eliminating the problems by use of...
forums.stangnet.com
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,
Click to expand...
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.

 

lojo1

Member
Mar 10, 2022
31
25
18
Charlotte, NC
Mar 12, 2022
#5
  • Mar 12, 2022
  • #5
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?

 

nickyb

I gotta say i never painted my nuts, Never Ever
15 Year Member
Apr 3, 2009
2,980
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nevada
Mar 12, 2022
#6
  • Mar 12, 2022
  • #6
Check/replace the cap n rotor while your at it.
 
Reactions: mattys91gt, lojo1 and General karthief

KRUISR

10 Year Member
Apr 16, 2015
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Mar 13, 2022
#7
  • Mar 13, 2022
  • #7
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.

Base Idle Reset

I'd like to post this for all the newer mustang owners and the others like me that never took the base idle reset seriously. I've had multiple engines and various setups but never once done the base idle reset. I just replaced the lifters in my car after having one collapse. I thought the...
www.stangnet.com

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).
 
Last edited: Mar 13, 2022

lojo1

Member
Mar 10, 2022
31
25
18
Charlotte, NC
Mar 14, 2022
#8
  • Mar 14, 2022
  • #8
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.





Added a little video of the car after the small changes.
 

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vristang

15 Year Member
Mar 31, 2005
4,933
101
124
Seattle
Mar 14, 2022
#9
  • Mar 14, 2022
  • #9
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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General karthief

wonder how much it would cost to ship you a pair
20+ Year Stangneter
Aug 25, 2016
27,959
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polk county florida
Mar 14, 2022
#10
  • Mar 14, 2022
  • #10
Reset the computer if you have not done so aready.
 
Reactions: lojo1

lojo1

Member
Mar 10, 2022
31
25
18
Charlotte, NC
Mar 15, 2022
#11
  • Mar 15, 2022
  • #11
General karthief said:
Reset the computer if you have not done so already.
Click to expand...
Will do, thanks!
 
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