I'm trying to figure out if my 350tpi is running right sometimes if I floor it off the line it will kinda bog or pause...almost like its is about to shut off! I think the injectors might be the cause...sometimes I have to hold the pedal down when I start it for it turn over. It gets bad gas milage too. Anyone ever hear of symtoms like this? When I turn the heat on I smell fumes and the car feels really weak under 2k rpms! Also should I be launching in drive or overdrive?

 

Try cleaning the intake and TB. Go get a can of throttle body cleaner, and spray everything clean. Sometimes a dirty throttle body and IAC will cause strange problems.

 

Get a fuel pressure gage and monitor your fuel pressure after you turn the car off.

 

The problem with doing what you just stated, hammering it from a dead stop, may sometimes be too much for the computer. Fuel injection cannot always react instantly, fuel injection especially factory style computers may do just what you mentioned. Stall, sometimes you need to get on the gas on a more linear curve, instead of instantly, because there are too many things for the computer to react to and it slows it down, try stalling the car out a bit, then nailing it, this is especially how you run at the track for better e.t's, and 60 ft.s

 

ok ill try that

 

No, thats not right. Any computer will act faster than a carb. There shouldn't be a bog. It could be a number of things; injectors, fuel pressure, timing, carbon in the intake, ect. Try checking these first. The beauty of fuel injection is instant throttle response.

 

timing and adjusting your Throttle Position sensor may help too. Its amazing what a simple tune-up will do for these cars and its not that expensive if you do it yourself

 

yeah.. double check the timing... I've had my timing retarded 2 degrees, and it ran like crap. It also had a slight pause everytime I mashed the pedal.

 

i have had the same problem as you... its real strange, couldn't go up my driveway unless i launched it... did fluid changes, new air filters, and i could go up, barely... i have yet to touch the IAC and the TPS though, too incompetant. I need to learn up some.

 

I just went through this. I was getting about 10 MPG and it was a DOG out of the hole if I floored it but ran fine otherwise. It was the throttle position sensor. Mine was bad so adjusting it would not fix it. I had to but a new one for $30.00 at auto zone.

 

I do not think it is because his computer is being to slow. It could be Acceleration enrichment or that part of the VE table is to low. Might be too large a throttle body? Possibly the fuel pump.

 

it could be a number of things besides the computer, but if you do hit the gas just the right way on a MAF sensored car, there may be a slight hesitation, and then it would go away. This may not be much, and it usually occurs from an idle on the brakes, in drive while then giving it a mash on the gas. But if its running rich, lean or tps is set to high, fuel pressure to high, it may also bog, gas and timing also effect it.

 

what about the mass sensor itself

 

same problem with my car. i have replaced the tps and set it exactly right and replaced and set the iac perfect. also i cleaned the throttle body and intake still no result. i have 42 psi at the turn of the key. would leaking injectors also cause this? becuase mine leak after i pressure checked the system.

 

Hey not to stray from the original topic..but has anyone heard anything from flow tech headers and y-pipe?

 

Try tapping on your MAF sensor while the cars running, if it starts to make the motor run rough, or bog or something, then you've found part of the problem, if it doesn't change the idle at all, The maf could still be bad, but not usually. If the relays are going bad, one of three can screw up the system. In my 87 iroc-z my iroc had one relay for the maf go, then another, and the car wouldn't start or anything, I disconnected the MAF, and the car started up off its pre programmed tables. I replaced the all the relays and I have had no other problems. Also if one of the relays goes bad, if you continue to drive with a bad relay, it will further damage the unit.

I summit tech associate told me flowtech headers and summit shorties and the dynomax/walker ones are all made by dynomax/walker, so buy the summit ones for the best price. So be prepared to have to tweak them a little bit.

http://members.cardomain.com/cronsformula

 

tweak them how? What y-pipe will bolt up to a set of hooker shortie headers?

 

By tweak them in terms of headers being installed, I mean, spark plugs might not fit in nicely, smashing into the primary tubes(big no no), buying more parts to install the headers to factrory exhaust. And usually the extra cost and frustration incurred while installing the cheaper headers is not worth the cheaper price. I have installed two sets of edelbrock headers one set on my 87 iroc-z(then I tuned 100 hp out of the car with that and some other things on the car. And the other set on a 91 z28. The nickel/chrome coated headers won't rust, they have nice 1 3/4" primary tubes, 2.5" collectors perfect for up to 450 horses and they help maintain high exhaust gas velocity. This when coupled with a good y like they have and exhaust helps make alot of power. As in my camaro, my first day there with the headers installed off the street I started at a 15.1 @ 89 mph, and tuned out 10 mph(100 hp) and brought the et down to a 13.8 @ 99 mph, within 11 runs from 4 pm to 9pm; with allowing the car to cool down in between runs. This also isn't bad considering I was getting 24 mph after this day at the track, and its a tune I can run 87 octane with no worry about knock, with 150K miles on my iroc. This car has made alot of people mad, considering I only paid 850$ for it, and had become a nice "beater."

My site: http://members.cardomain.com/cronsformula

 

The edelbrocks are not 1 3/4". Only SLP makes 1 3/4" shorties for our cars. So prove me wrong.

 

and the edlebrocks suck. Yes, I've had them.

 

Thats cool man what ever your trip is, I beg to differ, no problem though, they work great on my iroc, they helped me tune the best 10 mph out of her yet!!! This must obvisouly be because they are junk, and suck, then if they do, I'm loving them.

 

focus now.

 

its just lame when people put down what someone else has, just because they don't know how to get the most gains from them, so they sell them for something else, because of there own neglegence.

 

AS allways when starting to investigate these types of problems....

tune-up, tune-up, tune-up!

How many old parts ya got on there? Thats why cars dont run like new.

If you need help, look in a firebird / camaro repair book in the tune-up section to get an idea of what you would need to check / replace. Replacing 1 or 2 things like plugs or air filter does not qualify as a tune-up, you gotta have the whole package working good to have it run well.

Hope this helps get started

 

who was this question directed to?

 

I think the issue was that you said you had 1 3/4 edlebrock headers ....... the fact is you didnt you had 1.625 .....that was the issue. and yes Edlbrock do suck ....click my ww. on the bottom to look at better headers for these cars . Edlebrock welds were kind iffy when I seen them ....skinnier flanges ... pipe routeing made it a little harder to change spark plugs ..... this adds up to CHeap ...crappy ...product . But if YOU like them ....then thats all that matter ...right ?



To the origonal poster did any of this get your beast running better ? I spent a bit of jingle just on crap I can use to diagnose my problems with . Trust me ...its all money well spent . Like above fuel pressure guage , voltage meter , just for starters ...can help alot

 

Did you figure it out? You might have a bad cat. I had a lexus in the shop the other day that did exactly what your car is doing. Well does your car have a cat?

 

Last post on this page, those crappy, garbage headers with my 1.75", 1 3/4" primarys, let me tune out 10mph out of my iroc-z at the track, and I also received 24 mpg in the city, so it must be a buch of garbage. Thanks again, for your criticism, I'll take it with a grain of salt.

 

If you smell gas, it could be a leaking Fuel pressure regulator or a leaking injector.

have you tested your fuel pressure yet?

 

Like stated above, double check you're IAC and TPS. Also, with the engine idling, spray some carb cleaner around the entire intake area (everything prior to the MAF, the throttle body, vacuum lines etc..). Also spray where both sides of the intake manifold meets the cylinder heads)....

Holding the pedal down would only make matters worse if it were a leaky or clogged injector.... as pressing on the pedal allows more air (during the instance of the bogging you feel), not fuel (as when the ECM senses an increase in air, it supplies the proper fuel.... which soon smooths out the bog) , into the combustion chambers (during start up, and hard acceleration). If you're not getting adequate fuel to begin with (due to bad injectors), more incoming air will not help any (during start-up).

It sounds like just the opposite. You're not getting enough air into the chambers, and would also point to the reason why you smell gas... and have bad performance. You're running too rich.

If its the MAF, and/or the sensors, you're ECM should be throwing codes... which is why I'm leaning more towards a vacuum leak.

Are you throwing any codes?

Just my opinion by the way.

 

Wouldn't this cause a sporadic idle though as well?

 

If he is smelling gas, it could be from a leaky gas filler neck which GM had a recall on for these cars.