I have a 92 Explorer with serious backfiring problems.


After blowing out the initial muffler I had it replaced with NO engine work performed. It blew out the second muffler in about 1 week.

Before replacing muffler #2 it was discovered that many of the vacuum lines had collapsed due to trans fluid sucked up through the modulator, (Trans was rebuilt the previous month). Vacuum lines were replaced and the truck ran well for 2/3 week before starting to back fire again, subtle at first but quickly became serious. Lost muffler #3 within 5 weeks.

I just had the truck in the shop and the mech said that there were issues with the TPS, IAC and PCM.

Now to my question: How do I test these myself, if they are bad is it worth my $ TO REPAIR THEM, (Truck has 150k), Lastly does it make sense to tackle any one of the issues before the other? One more, are these issues that can be handled by the average Joe who knows about engines etc. but is no mechanical superstar, or star or even moon rock.

Much gratitude to anyone who can shed some lite on this for me.

Jeff

 

IAC, you can try and clean it yourself or replacement is very easy. Here's a link to help you out.

https://www.ford-trucks.com/article/...r_IAC_Fix.html

The PCM is located behind the plastic kick panel front passenger side near the floor. If the PCM is indeed bad, you can pick one up on ebay or your local bone yard. Just remember you'll have to match up numbers on the PCMs.

Can't help you on the TPS but I don't think it's too difficult, some one will chime in on that one soon enough.

Stupid question......did you get the modulator valve replaced?

 

I don't think the TPS or IAC would cause (what I assume is some sort of problem with unburnt fuel entering the exhaust system) the problem you are having. Maybe the PCM would. Did the mechanic give you the actual codes that it's throwing?

 

NO, HE DIDN'T GIVE ME THE ACTUAL CODE. I suppose it would be a good idea to try and get IT though.

 

backin72: Are you suggesting that I replace the IAC valve with an aftermarket AND clean the air supply system also? Yes, the Modulator was replaced with the Trans rebuild.

marragtop: I agree the backfiring is probably due to unburnt fuel entering hte exhaust system. I was originally concerned with a sticking or burnt valve and should do a compression check, but the passanger side spark plugs are a real pain, and power dosn't seem to be an issue like I would would expect with bad compression, for any reason.

Are you suggesting that the PCM might be controling mixyure, or delivery or something like that, thus causing back firing? Would that be related to 'RUNNING ON' or 'DIESELING" as well?

If I replace either of these components are there additional adjustments or settings that need to be made to accompany the replacement. I have heard someting about a "Keep Alive Module" in the past but am not sure what that is?

Thanks to both of you for your insight, I will let you know wat the results are.

 

You should really get the codes before throwing parts at it. Most autozones will pull them for free. Get the codes and post them here. IF the PCM and/or TPS are bad, they should throw codes. There can be codes stored even if the CEL is out. DId all of this start before or after the trans rebuild? If you are also having diesling/running on, I suggest checking the fuel pressure at the rail. Also, the plugs are easier to get to through the wheel well. You're going to have to get to those plugs eventually, as they are probably somewhat fouled at this point.

 

DITTO to what marragtopp sez. Before you blow up something more than a muffler, get the trouble codes.

When my Ranger was backfiring, i hooked up my Actron scanner(30 bucks at Autozone) & in 2 minutes I knew the ignition module was shot. Replaced it & no more backfiring.

Not saying this is your problem, but it might be.

If you hookup a vacuum gauge, you will know in a couple of seconds if you have a "burnt or sticking valve."

A vacuum gauge will also tell you if cam timing is whacked.

If you have low vacuum caused by a leak in a vacuum hose. The vac gauge helps you find it. Just pinch off hoses at their source til the reading comes up.

Bottom line pull the codes yourself, 30 bucks for the Actron scanner or get the codes from your mechanic.

The reason that I mention the Actron CP9015 scanner is that it comes with excellent/easy to follow instructions for how to use it & lots of good info on how your EEC-4 engine controls work. It's also dirt cheap.

Not all scanners include this info.

Btw, if it's dieseling, that might be caused by the trans fluid that was sucked into the engine.

If the combustion chamber is carboned up & the carbon is glowing red hot, that can cause dieseling.

I'd cure that by giving the engine a glass of water.

 

Thanks, I didn't think about the fuel pressure... I will check that.

I am goung to get a code reader ALSO before doinf anything else.

I did get a can of Seafoam today, it is a cheap option andcan't hurt in any case. If Trany fluid is in the combustion chamber it should help to clear it out also.

I have never troubleshoot using a vacuum before so I will have to read upon how to do that.

If my CAM timing was wrong, wouldn't that cause poor performance other than back firing?

87XLT; can you explasine your suggestion about water?

Thanks all, I will get a code reader this weekend and see whati t says.

 

Jeff, heres a link that explains the water trick http://draco.acs.uci.edu/explorer

Click on engine pinging & read the post from Bobm

The main thing about using the vacuum gauge is it gives you a pretty good idea of what shape the engine is in & if you get lucky it might even point you in the right direction to solve a problem.

 

Marragtop is right about stored codes even though there is no CEL. (I cleared an erratic throttle issue after running a test which pointed to the TPS...I had no CEL). That's a different issue than what you have, but I wanted to give my 2 cents and subscribe to this thread...I'm interested in the outcome....

 

I used a can of Seafoam last night. Inserted it through the Brake Booster Vacuum. If seems to have a little more zip to it, but made no real difference in the running on.

Here is an interesting tib bit. Last week it was so bad that I didn't want to drive it any where becouse it backfired and ran on everytime I shut it down, without missing a beat.

the last couple of days I have driven short distance (10 miles) and it shut of without a hicup. When I drive longer it runs on. now it seems to be a 50/50 chance that it will run on.

Hmmm... starting to sound more like an electrical thing to me? Can't wait to get a code reader this weekend.

 

I checked the Vaccum today, read 21.5 inches and fluctuates about 2 CM or less than 1/2 in at a slow consistant rate.

The manual suggests an exhaust problem. Of course the muffler is blown wide open so there is NO blockage there. However I noticed that the previous owner actually drilled a hole in the cataletic converter, (to make it sound better). Could that have an effect leading to running on or back firing?