[thomaspatton]

You guys might hate me for this, but I want to post this here in hopes that someone who's added performance parts to a Mustang can help me. As far as my expertise goes, it's only in keeping OE Engines running good enough to drive. So, any help you guys can give I'll take to heart. Anyway...

I bought a 91 GT from a guy. He seemed pretty knowledgeable on Mustangs and said he put on:
Cold Air intake [confirmed]
Hi-Perf Radiator and Electric Fan [confirmed]
Catback, no Diameter increase [confirmed]
3.73 Rear gears [unconfirmed]
Performance Cam [specs unknown]

Here's the thing though. Car ran great until I did ONE thing. He never ran an "ignition hot" lead to the Radiator fan, just spliced it into the interior defrost wire. So you had to have the defrost on for the radiator fan to work. I unspliced it and fed it into a hot ignition lead under the hood. Since then, the engine seems to be on the fritz. No, I didn't splice it into the ignition coil...

When it's cold, it starts fine, but then drops idle and dies, unless I constantly give it gas. Cold tempered maybe. I even took the intake apart up past the throttle body and cleaned it. No help there.

When it's hot, it idles high. Normal idle is around 1600-1700RPM. I've tried lowering this through distributor timing and if I drop it down lower I get either horrible backfiring or the engine dies. I've heard that +/- 10° after installing a perf cam is normal, but I'm not even getting anywhere close to that on the harmonic balancer. I've turned to not even looking at marks to time it and going by ear and RPM.

Just recently it's started a popping sound during acceleration. I haven't been able to pinpoint where exactly, but it's from somewhere under the hood. It sounds like when you pop the top on a jelly jar, only I can actually feel it through the floorborad as well.

So, Just for this problem, do you tech-heads have any ideas that can help besides a Crate engine and running gear overhaul?

*edit* Also, if that wasn't problem enough, I'm noticing a knocking noise at a particular RPM. When the engine's around 1700-1850RPM I get a knocking/thumping noise that seems to come from under the floorboard. Any idea what that could be coming from?

[neverfastenough]

Ok I started a reply, but needed to know first if it is an on all the time fan or thermostat controlled? An on all the time fan draws a lot of power and hooked to the wrong thing can have a drastic affect on the electrical system. Second, I am sure you know this, but in an effort to make myself sound smarter than I am, did you put coolant into the rad when it was cold? Sometimes a air pocket will form and cause a slapping sound in the coolant system. I would try to find a different source of power to see if it is whats causing the problem. Disconnect the power wire run a wire to the battery and see if it still has the same problems, if not then you are drawing too much power from that system. P.S welcome to the site!

[dr.gonzo!]

Put the timing back in the normal range. Dont use timing to adjust the idle, there is a screw under the throttle body for this. Did you clean the IAC? If you did then look for a vac leak. That knocking you hear is becuase the timing is way off. But if it is coming from the exhaust then you have an ignition problem because that is wasted gas hitting a hotspot and igniting.

[thomaspatton]

Originally Posted by neverfastenough ...if it is an on all the time fan or thermostat controlled?

It's on all the time when the car is running, however I've neevr had an issue with anything electrical since I've hooked it up until the window situation. Today I went out and took both window motors out and cleaned them but still not working. I can't get an ampmeter atm, so I can't check the circuit, but even so I don't know why it would just stop working out of nowhere.

Originally Posted by neverfastenough ...did you put coolant into the rad when it was cold?

Yeah, but I always run it a couple seconds before putting the cap back on. Also, just a side note, I noticed after actually LOOKING under the hood that the guy who I got it from routed the belt wrong around the water pump because he took the Air Pump off and didn't install a dummy pulley. So I think I might have found part of my overheating issue.

Originally Posted by neverfastenough Put the timing back in the normal range. Dont use timing to adjust the idle, there is a screw under the throttle body for this. Did you clean the IAC? If you did then look for a vac leak. That knocking you hear is becuase the timing is way off. But if it is coming from the exhaust then you have an ignition problem because that is wasted gas hitting a hotspot and igniting.

If I put the timing back into normal range, even with throttle body screw adjustments, I get horrible backfiring on acceleration. It's not a fuel issue, I don't think, becuse filter is new, pump works fine, and I put 93 Octane in it just because. I got it a little better today, but I'm still getting the knocking within the 1700-1850 range. I took the IAC completely apart and cleaned it a couple weeks ago when I cleaned the entire intake system, so it's not sticking at all.

If I hear it coming from the exhaust should I check my spark plugs, distributor, and everything in between? If it's due to timing, how can I get my timing to drop back into a normal range without the sputtering and back firing?

Thanks for the help so far. I'll get this fixed sooner or later... probably just in time to have to rebuild my transmission or replace the starter or something else, who knows.

[dr.gonzo!]

No what I ment was you have and ignition problem. the backfire noise you heard was unburnt gas hitting a hot spot and going "bang" its obvious you are not having a fuel problem or else it would never get the chance to backfire becuase there wouldnt be any gas to explode.

[dr.gonzo!]

[quote=thomaspatton][quote=
If I hear it coming from the exhaust should I check my spark plugs, distributor, and everything in between? If it's due to timing, how can I get my timing to drop back into a normal range without the sputtering and back firing?

[/quote]

if it is backfiering check everything from the firing order, distributor, spark plugs,coil, compression, check for spark on each wire, look for worn wires. If you want it to put the timing back to norm w/o it backfiering fix the ignition issue.

[thomaspatton]

[quote=dr.gonzo][quote=thomaspatton]

Originally Posted by If I hear it coming from the exhaust should I check my spark plugs, distributor, and everything in between? If it's due to timing, how can I get my timing to drop back into a normal range without the sputtering and back firing? [/quote if it is backfiering check everything from the firing order, distributor, spark plugs,coil, compression, check for spark on each wire, look for worn wires. If you want it to put the timing back to norm w/o it backfiering fix the ignition issue.

Thanks for the help. My biggest issue with the timing was that I forgot to remove the Spout Connector... Sometimes I'm a retard...

As far as the Popping sound, it's gone now that I've fixed the timing. I'm still getting the knocking sound at constant RPM, though, and have pinpointed it to the exhaust, close to the muffler on one side. It's not a loose muffler or anything like that, so I guess my next big step is changing Spark Plugs and Rotor Brush since the cap and wires are fairly new.

AND, something else I noticed since the wind happened to blow the page in my manual open when I was timing. The guy removed the Air Pump, which is fine, except he didn't put a dummy pulley on it, shortened the belt, and misrouted it around the water pump, so now my water pump is running backwards. I plan to fix the belt ASAP, but was wondering if running it this long has caused any long term damage to the Water Pump? The car luckily hasn't overheated, I'm just worried that the Water Pump running backwards for so long has had an adverse effect on it.

[dr.gonzo!]

I removed my air pump w/o a dummy pully and bought a shorter belt. all I did was took the belt tensioner off and drilled a new hole on the bracket and rotated counter clock wise. pretty simple to do, but hard to explain.

[ScratchinFerTraction]

The water pump should run backwards on a 5.0. Check this link out for various belt routings and lengths. I would fix the fan so it is controlled by the computer or a thermostat sending unit, basically like stock. I have a 347 stroker with a stock radiator with stock fans (95) that runs fine even while sitting in rush hour Philly traffic.

http://www.moddedmustangs.com/forums...hlight=routing

[dr.gonzo!]

I almost forgot...You have an aftermarket cam. the timing may need to be adjusted to diffrent spec other than what the haynes book says

[thomaspatton]

Originally Posted by dr.gonzo I almost forgot...You have an aftermarket cam. the timing may need to be adjusted to diffrent spec other than what the haynes book says

Yeah, I have it set to +13º right now. I'm not getting any popping, great throttle response at the pedal, and steady idle at 1600RPM with the throttle adjustment screw all the way out. I'm still getting the knocking sound coming from the exhaust system, but I don't have the funds for new plugs atm.

once again, thanks to all of ya'll for the help.