Hello Again

I am trying to pinpoint this issue with my 350. It was garaged all winter and unfortunately hardly started at all during that time In the Spring it ran very rough and junky.. fuel additive and dry gas cleared most of this up, but this problem remains:

It has a rough idle (car is shaking) and when you first give it gas it feels like it's going to stall, but doesn't. It does not surge that I notice, though.

When accelerating it feels fine and I'm not noticing any issue with pickup, but when maintaining speed or slowing down I can feel light surging.

If I'm on the highway and take my foot off the gas completely, sometimes it will make a popping sound or two.. it doesn't really sound like backfiring and seems to be toward the front of the car/near the pedals.

After driving around and getting the car running hot, Emissions test still shows HC and CO readings are 2-3 times the legal limit, NOx is like 1/4 of what the legal limit allows.

Oxygen sensor has been replaced... fuel filter and spark plugs were a bit gunky and those have been replaced. However, the issue remains. One guy said I needed to take it out and drive it like 100mph and clear it out but I'm not sure at this point that's going to help. I have driven it quite a bit and don't want to exacerbate the issue.

Any ideas?

 

sounds like EGR valve or a leaky fuel injector

 

Kinda like this with the shaking at idle, does it do it when its cold to ? or just when hot ? : https://www.thirdgen.org/forums/tpi/...ctors-now.html

 

advance the timing about 2deg

when you move the dissy see how far it moves from on side to the other before a shift in timing

if it is any more than 6deg put a chain in it

 

Thanks everyone for replying

I will have them check the EGR valve and fuel injectors.. I hope it is a matter of them just needing to be clean!

The rough idle shaking is only when it's warmed up.. although when when cold the idle sounds like it's surging a little.

I will ask them to check the timing as you said... unfortunately I have never worked on my car and don't have the first clue what I'm doing

Thank you again..

 

Ya, I had similar problems, injectors and timing were issues with mine...if you have a ohm reader, unplug each injector one at a time (plugging them each back in after you check it) and do this when the engine has run for at least 7 minutes driving around so that its good and hot. when the injector is unplugged, you will see two prong-type things in there. you will touch the negative part of the ohm reader to one prong and the positive to the other prong, doesn't matter which one you put them on. I believe they should all read between 12 and 16...not sure. but if you notice one under 10, you have a bad injector. what Im thinking is its mostly timing. that lil jolt or pop you feel when you take your foot off the gas is normally a timing issue. if your timing is up real high, it will cause your car to run richer because the engine is running harder.

 

Other thought: TPI engines have a cold start injector on the left bank. At least my 305 did... It sprays in extra fuel when cold & cloeses engine is warm. If its stuck open the engine will run rich & could cause some of those problems.

 

Cold start was removed after 1988 so 1989-> dont have the 9tn injector, they spray more on all 8 at cold starts.. just to all the 1989 and later models

 

EDIT: dealership b*tching removed..

OK it appears 4 of my injectors are bad (reading like 6-8 ohms). I guess this can cause the rich emissions..

My car has an aftermarket cam, underdrive pulley, headers, a chip and some other minor engine mods.. should I go with 24lb injectors? They've already quoted me about 500 bucks to replace all 8... I dunno what they're gonna stick me with if I ask them to adjust the computer for 24lb ones. Having them run rich is not going to be good because that's what I'm failing emissions on Should I just go with 22lb?? I was looking at the pink top Bosch/Ford injectors that I've seen mentioned here. Thank you very much for any advice!!

 

I should add I'm planning to go with a 3" catback system in th near future as well.

It's almost impossible to find 22lb... If I do 24lb ones is there going to be a big problem if I don't do the chip burning too, given the above mentioned mods?

And if 24lb is OK.. what is the difference between

http://store.summitracing.com/partde...5&autoview=sku

and

http://store.summitracing.com/partde...5&autoview=sku

besides 100+ bucks??

Thanks

 

They cheaper ones are not flow matched..

I would buy these injectors instead : http://fuelinjectorconnection.com/sh...&productId=134
They are the BEST injectors on the market today, they have a great spray pattern and they flow exatly the same.. I got the Ford injectors on now (Denso made ones) I will change them to the ones from fuelinjectiorconnection in the coming weeks. After I seen them flow and spray . So Go with these ones instead, direct fit.

Ford ones are little shorter and may need change of O-rings to seal 100%..
and the Ford injectors are rated at 39PSI of pressure, the Bosch III are 44psi = much better.

 

I've never heard of that company while searching around. Are there issues with going with rebuilt vs new?

The car already has a Hypertech chip in it from way back.. might it compensate for the jump from 22 to 24lbs? I just want to get my car running again and don't want to have to find someone to burn the chip after..

Or should I go with these 1985-91 Corvette Bosch 0280150556-D5B - GM New - Flow Matched Set $305.50/8 Set http://www.fiveomotorsport.com/Injec...sTPI.asp#caddy

 

You got 3years warranty on the rebuilt ones, and Jon is really great to talk to, They will not fail. I will promise you that.

They flow 22lbs as stock so no need to adjust the PROM.

I would buy the 169,95 any day!

 

Well I bought a set of them from him through eBay so we will see how it goes!

 

Keep us posted

 

Jon is great! The injectors are really nice. The car is running awesome now and I saved a little over 100 bucks, so all is well Thanks!!