I've made a previous post about my engine running really slow after my cam/headers install. I have done about a million searches on the forums and still haven't pinpointed my problem.

I installed the SUM-1065 cam 216/216 duration @ .50 .454/.454 lift 110 LSA

I installed headman headers with thrush turbo mufflers. I have yet to put the o2 sensor back into the headers. I still need to weld a bung to it and get a heated o2 sensor.

I installed the Stage 2 Performance Chip from Harris Performance. (recommended by many from this forum)

Here's my trouble. The engine sounds really good and idles are 600rpm and sounds very strong up until about 3,000RPM then sounds like it's missing or something.

My fuel pressure is right around 43psi and vacuum is around 11-14psi. I installed a 3.9k ohms resister to replace the knock sensor.

I advanced the time to about 10 and it seems to consistently increase to about 30 or so at 3,000rpm.

I just checked the valves again and lashed them and that doesn't seem to be the problem.

The only engine code I'm getting is 13 (due to lack of o2 sensor on the exhaust I'm assuming)

The engine feels like it just has no power...about the same power as my daily drive dodge neon lol. It won't even spin the tires when it could spin them very easy before all of this engine work. Any ideas on what's going on?

 

I just replaced the fuel filter and the ignition module and it's still dirt slow. It misfires like crazy and I have no clue why.

 

Im having he same problem with my car, im thinking vacuum leak or the timing?

 

I don't think that there is a vacuum leak in my case. I checked it and it was around 20 vacuum I believe. As for timing, I have it set at about 10 BTDC.

I just replaced my cap/rotor/spark plug wires with MSD and it fired up almost instantly. The engine sounded solid but I couldn't go for a test drive last night...it was kinda late and I didn't want to **** the neighbors off haha

If that was the fix to my problem, I'll be sure to tell you.

 

Just went for a test drive and the car runs a little better but it's still slow as hell at WOT. I'm starting to think that with all of the mods I have, I'm having a lean misfire. I saw where you can make a homemade AFPR pretty easily so that's what I'll be doing tomorrow!

 

You have not said what Engine and what year TPI that you are running. Are you running a Speed Density or MAF System? What ECM? This information is needed if you want the best answer. 85-89 systems were MAF and 90-92 and 91-93 LT1 were Speed Density. If you are running a Speed Density system, I would say that the camshaft has too much duration, but that is just an educated guess. SD systems are especially sensitive to long duration and high overlap camshafts. Your fuel pressure is 43 PSI with the engine not running? Or 43 PSI at idle? 43 PSI at idle with 14 inches of mercury is actually over 50 PSI. With the FPR line hooked up, the Fuel pressure is inversely proportional to the manifold vacuum. So when you have low vacuum the fuel pressure rises and when you have high vacuum, the fuel pressure lowers. The job of the regulator is to maintain about 42 PSI differential between the fuel rail and the intake manifold. So when the engine is at WOT and manifold vacuum is near ZERO, you must have about 40 PSI pressure at the rail. Conversely, when the vacuum is high (say 20 inches) the fuel pressure in the rail DROPS to 32 in the rail. Since 20 "inches" of mercury is about -10 psi you still have the 42 PSI across the injector. If your regulator is stuck or not hooked up, when the engine is in a "High vacuum" situation, the fuel pressure will be too high. The ECM will miscalculate the engines' fuel needs based on the the screwed up fuel pressure and the acceleration shot and other parameters will be all screwed up. The GM ECM was built for and depends on the O2 sensor for many of its functions. The O2 and either the MAF or the MAP are the two most important sensors in the system. Operating the ECM without an O2 sensor forces the ECM into open loop, OPEN loop pretty much puts the car in "Warm up" mode all the time. This ECM DOES NOT "like" being in open loop. The ECM functions best, ESPECIALLY in the mid-range and at cruise in closed loop. The ECM gets signals from all the other temp sensors saying, "this car is hot and should be in closed loop", but no O2 sensor signal tells the ECM something is wrong. The ECM cannot calibrate itself without the O2 (and all the other inputs) and thus will not operate correctly in the WOT position either, regardless of the chip. I would install a heated O2 sensor and check the Fuel pressure to make certain it varies in direct proportion to the manifold vacuum. Have you checked the TPS voltage? Should be 5.0V reference and .54 volts with the throttle closed and increase smoothly as the throttle opens to almost 5.0V at WOT. Search this forum for "TPS voltage" there has been a lot written about this subject.

 

Sorry I didn't include the engine type.

305 TPI MAF (The block does say LG 5.7 though, but the injectors are 19lb and the intake manifold has a 1985 date and they only had the 305 that year from what I understand).

I've checked the TPS .54 volts and around 4.5 volts at WOT. I installed an o2 sensor in my header finally so that engine error code is gone.

I've replaced the injectors with Ford 19lb injectors.

I'm seriously completely stumped on why there's no power and why I'm getting almost like a lean misfire over 3,000 rpm.

So frustrated....I'm about to just sell this car...

 

I also installed a 3.9k resistor in place of the knock sensor but still get an error code for that (42 and 43 sometimes). I just bought a new Electronic Spark Control Module that I'm going to pop in tonight.

Any other ideas on the "lean" misfire at WOT?

Another to add: I never replaced the valve springs when I swapped the new cam and lifters. I'm starting to think that the stock valve springs are really warn (assuming they've never been changed) Which is causing valve float. I know you aren't suppose to get valve float till higher RPM's but I know TPI systems run at lower RPM ranges so I ended up buying a kit of valve springs.

http://www.summitracing.com/parts/SUM-174000/

Even if this doesn't solve the problem, I should change them anyways.

 

Are you running the 1985 1226870 ECM or the 86-89 1227165 ECM? What Vehicle Speed Sensor are you using? Does it misfire in all gears at all speeds or does the misfire come in at higher road speeds? Does the spark advance when you rev the engine? Have you tried a new Ignition Module? I am running 19 lb FORD SERIES 3 injectors without any issue. Were the injectors new or recently cleaned?

 

Running the 1985 ECM. I have a Stage 2 Chip from Harris Performance. My VSS engine code (24?) came on the other day but quickly went away (First time it's ever done that). It misfires at any gear. And yes the spark does advance.

I installed a new Ignition Module about a month ago. no luck.

 

is it a 305 or 350? did you break the cam in right?

 

It's a 305. I believe I broke it in properly. I added a bottle of the break in liquid in with my oil and had the car run around 2k for about 10-15 minutes.

 

get to o2 sensor hooked up

 

Got it hooked up now. I have to connected at the bottom of my header where all of the lubes collect together.

 

shortys or long tubes

 

long tubes I believe.

http://www.summitracing.com/parts/HED-68460/

 

Does it misfire then you "free rev" the car sitting still in park? Or does the misfire appear only when the car is rolling at speed? Is your speedometer accurate? Or is it showing like 100 when you are going40- 50, with the 410 gears the speedometer should be WAY off, unless it has been re-calibrated for the gear change.

 

need a heated o2 in long tubes

 

The speedo is way off, but even before I had the 4.10 gear in it. When I was going 55MPH, it said I was going 70. I'm sure the speedo is messed up...giving me code 24 (only once)

 

Remember that the speedometer controls the speed limiter in the chip based on the VSS signal. Some Chips are set with the speed limiter (fuel cutoff) at something like 110 (depends on the car, gears, trans and the tires). When I fired mine for the first time on the jack stands it would rev like a demon to 5000 or more in neutral. I put it in gear and ran the transmission through the gears, my speedo was off like 40 mph. Car had 2.42 gears and a three speed. I put in a 200-4r overdrive and 3.42 gears. Long story short, at 45 the speedo was at 85+ so I am running it just to heat it all up and as the tach hits 3100 in 4th gear (overdrive) the thing starts popping and bucking like it has blown up. Scared the CRAP out of me, since it was all Brand new! Unhooked the speedo, ran it through the gears and the "misfire" went away!

I need to have the chip burned to raise the speed limit to match the gearing. My car uses a cable speedometer and an inline 4K pulse VSS to tell the ECM how fast we are going! After changing the speedometer drive gear to the largest available, I am still off by about 18% too high. At 55, the speedo indicates 65 so when I hit about 100 actual (GPS) speed the engine hits "fuel cutoff" on my stock AXXB chipset. At 100, the ECM thinks the car is going 118, which is the OEM Fuel cutoff for this chip (so I am told). If I remember my F bodies, your car uses an electronic speedometer (no cable) and the VSS tells the ECM how fast you are going and, in turn the ECM drives the speedometer. You have low gears and if your chip has the fuel cutoff set at a really low speed, then you could be running into the fuel cut-off even in the lower gears. Also, if the VSS is sending an incorrect signal or no signal the ECM could be fooled by this as well.

Do you think this might be what you are experiencing?

 

This could be very well be the situation. The only thing is, before all of my add ons (cam and full exhaust) the speedo was off by a lot and the engine ran completely fine.

I'm going to replace the valve springs, boost up the fuel pressure and replace the ESC first and if none of that fixes it I'll look more into the VSS. Thanks for the heads up!

 

You said that you put the o2 sensor at the end of the headers. but on a stock manifold isnt it just in one exhaust port off of one piston? so if thats the case you would be running 4 times as much exhaust through it?

 

just reading along, but i seem to be having the same issue... but mines 350 carbed, accell hei and module upgrade, rpm airgap, 1406 600 edel, shorty headers. i dont have a timing gun so i did it by hand to get it to start as soon as the key turns. idling will rip up to 5500rpm no problem, but when i took it around the block around 3000 it was missing. would it be to lean or would the distributor be out? away from work on my car right now and cant try it to point you guys in the right direction atleast....

 

I'm still in the process of figuring out the problem. I replaced the ESC Module and finally replaced my valve springs to a stronger spring. I haven't taken it for a test drive yet, but tomorrow I'll find out if that was the problem. Are you getting any check engine lights? Try the old paper clip trick and figure out the codes if any. We can troubleshoot from there. Hopefully we can get our cars both fixed. There's too many mustang around my area thinking they can keep up with my camaro

 

its driving me nuts, with my job im 3 weeks on 1 week off and i got 2 weeks left till i can try. as for engine lights i have everyone in the book on cause my computer is hooked up but im just running starter/ingition and alt, have aftermarket gauges but im running a carb, my dad thinks its the timing, but my carbs is on the lean side i believe.

know all about the mustangs my roommate bought an 86 5.0 5 speed i swear to just **** me off lol threw my car together pretty quick but wanna shut him up so bad lol

 

haha Same with my friend...he just bought a 95 5.0 mustang and thinks it's the fastest thing on the street lol You can adjust the timing pretty close by just hearing the engine. You MIGHT be able to loan one out at Autozone. Otherwise I'd suggest you spend the 30 bucks and buy one. It's well worth the 30 bucks. You jets on your carb might need some adjusting as well. If you have a lot of engine mods, you might have to bump up the fuel pressure. What size is your carb? I'm sure with a mildly built engine a 650 or 700 would be plenty big enough.

 

funny all rustang owners think that? lol ive been talkin to my cousins boyfriend who is into cars and his brother has one hes gonna bring by. I dont have much for internal mods, it was a 400$ 350, but everyone asks if its cammed. might have an rv cam if that, but its a 600 edelbrock 1406 (economy), but have a jet kit and an advance curve kit for my dist i just gotta play but like to read up on the best way to do it when i cant, in calgary to so have a high elevation too

 

Recheck the timing. It should be at 6*. Make sure the spark plug wires are correct. The most important thing is to get the O2 sensor working. It tells the computer if its running lean or rich. Thats very important! Do this first.

 

A little update on my camaro. I made a homemade AFPR and the problem still consists. I'm going to get a fuel pressure gauge tomorrow and make sure it's actually increasing the fuel pressure.

Could my cam be the problem? I know people say LSA 110's are bad for TPI's but I can't imagine in would cause this big of an issue to run like complete crap at WOT. The car runs great when you're just driving around regularly.

Also, could the fuel pump being going bad? Its been making kinda weird noises when starting up since I made all of the upgrades. Would a fuel volume test determine if the pump is going bad?

I'm currently getting no engine codes, so that's good at least.

Also just replaced all of the valve springs to some stronger ones (300lb close I believe?)

Any other ideas?

 

well im not huge into fuel injection, but i know the basics, is the fuel pump stock? you might need somethin a little bigger to fuel the beast if it is, and its 25 years old

 

I have no clue if it's been replaced but I'm assuming it hasn't. It's probably on it's last leg. Looks like I know what I'll be doing next weekend.