OK, I've got a 4v mark 8 engine in my 99 GT. Been running fine for about a year now. Just installed 98 cobra intake cams and cobra intake manifold over the weekend. Put it all together and started right up. Took it out for a drive and it hesitates under load. I set the cruse at 60 and it coughs and sputters til I down shift. Mods are email tune, CAI, full length headers and off road H pipe, EGR delete. O2 sensors are installed. Any ideas?
Hesitation After Cam Install.
- Thread starter Bford
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Things I've done: checked for codes and nothing, tested coils,all good. Made all new vacuum lines. Used carb cleaner to check for leaks and nothing. Tested the TPS and its at 0.97. I'm going to rig up a fuel gauge and test the fuel pump under load tomorrow. Is there anything else I cam test.
The email tune. I did a cam swap in my old 96GT and it ran awful on the canned tune. Cleaned it up with a custom tune. How does it run without the tune?
squeak93
15 Year Member
+1 on scrapping the canned tune. Find a reputable tuner close and get the most out of your combo.
Anyone know a good tuner around the Peoria,IL area?? Herring Perf. said they ONLY do GM's?? What is this the 1970's?? Reline Perf. in Bloomington IL said they don't use SCT?? I dont want to go buy a Diablo when my SCT is fine. I haven't heard too many good things about Dillon in E Peoria. Don't really want to go to Chicago to get a tune.
squeak93
15 Year Member
STL Mustangs is a few hours away from you. Bob Monks is the man.
I drive 5-6 hours (will be headed that way on the 23rd) to see him.
I drive 5-6 hours (will be headed that way on the 23rd) to see him.
Before I get a tune, I want to make sure that's what it needs. I don't want to be up there turning wrenches while I'm paying someone a hundred bucks an hour to watch me. I did a compression check to see if one side was WAY different then the other. Both sides are between 150 and 160. I think that should be about right for a 75,000 mile engine. I took the tune off but then it wouldn't let me change for gears, tires, egr delete,..... Let's say I am a tooth off. How much timing does the computer have? How much timing does one tooth equal too?
squeak93
15 Year Member
If you're one tooth off you'd have compression issues from side to side, as well as possible PTV contact.
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Update, While performing the compression test, I noticed some plugs were sitting in oil. I cleaned everything up and installed new NGK TR55's. When I buttoned everything back up and started to prime the fuel rail. I noticed the walbro 255/lph fuel pump was a lot louder then I remember. Took it for a test drive anyway. It was better but not quite there. Put a new Focus SVT fuel pump part # E2386 from advanced auto for $69.99. That did it. So looks like I had a couple of things going on. Still going to get it tuned, THX for all the help!!
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Updated Update. Got back late last-night from Redline Performance in Bloomington,IL. Danny Biggs (Retired from Anderson Motorsports in Clinton) was doing the tuning on my car. He could only get 293 HP out of it. (@345 at Flywheel) A little disappointing. The problem was he couldn't get that with Back to Back pulls. 1st pull was done cool (170*), the second pull was done right after 1st pull(195*). The tune would drop 7+ degrees of timing at 4800 RPM's resulting in a 50 HP loss on the second run. If we left the tune alone and let it cool back down to 170ish, It would repeat the 293. Anyone have an idea what would cause tune to drop timing with 20 degrees hotter temp? I was wondering if the Mark 8 temp. sender in the cross over tube was calibrated different then the 99 GT. Any input will be greatly appreciated.
