Rough idle hot and cold.

Drives fine at low throttle.

Some surging at highway, kind of like on and off the gas sensation. This recently started along with a sucking restrcited type sound from under the car.

One bank of engine(pass) is not nearly as affected if I pull plug wires or injectors.

Horrible hot restarts.

Did have a dead cylinder on pass bank I was forced to drive home on summer break(1100 miles,not completely dead but almost)

Im not at home, at school so regular garage and tool selection limited for testing.

It does have new injectors and wires on it, along with testing coil and good cap/rotor before anyone asks lol. Swapped out my back up ignition module.
No codes and everything looks good as far as the drvr bank is concerned on the laptop.

I have heard strange exhaust noises as well, like when its trying to blow out at the next least restrictive place, but it went away and I thought I was imagining stuff.

Also keep in mind it is a dual cat car, so one cat down wouldnt kill it completely.

Share some thoughts with me people

later and thanks
Jeremy

 

19-20 inches vacuum at idle.

If I rev it to 2-3k it goes to 15 and then increase back to like 23 inches very quickly.

I cant find the test for restricted exhaust on a vacuum guage and I know its here somewhere.

Of course if one bank is plugged the other cat could still be good and vice versa

Any help

later
Jeremy

 

Drops to zero when I rev it.

Unhooked a.i.r. check valves and back pressure tested it was under 1.0 at idle and maybe hit 1.5 revving.

From this it suggests the cats arent clogged.

Going back out to run fuel pressure tests next. Did notice some weird surging and hesitation yesterday when I purposely took it on a highway road trip

This is just getting annoying

Vacuum is 19-20 inches steady, with maybe a .5 variance at most.

I hate fixing everyone elses junk and cant make my own junk run right.

later
Jeremy

 

does it drop to zero & stay there?
dual cats make it hard to test with vacuum & they could possibly affect exhaust back pressure because of the exhaust crossover. if the intake was split side to side it would be pretty easy to check.
if both cats are clogged, the vacuum would decrease toward zero when you rev it up & hold it around 3000 RPM. if one cat was clogged you would be noticeably down on power, but it would probably idle fine.
what your describing sounds to me like the cats are ok.
the only dual cat systems i remember checking for a restriction had dual exhaust, so we could just see if we feel a difference in exhaust flow. if we couldn't tell if there was a difference, we pull the front O2 sensors & see how it does on the road.
did you hear any rattling.
i know this is something you don't want to hear, but you may need to drop the cats & have a look inside them to be certain.
i wonder if you may have gotten some bad gas with all the rain we have been getting in the last few months.

 

Thanks for replying.

I understand what your saying and I agree but I dont, kinda just like u said.

Datalogged it while out t-nite.

Still will surge on the highway, real lite , barely enough to notice, but nothing shows on datamaster.

Lowest observed blm was 117 decel and coming back on gas, at any highway cruise, it was 121-130. Absolutely nothing shows wrong on the scanner and remem the o2 is on the drvr side as well. That also pretty much rules out low or high fuel pressure as well

One thing I did find funny was at steady speeds the map reading was higher than usual, not alot, but definitely noticeable, it also was when i dippped in the gas slighlty to accelerate gently. Do I have one cat restricted and choking it back some and its only noticeable under load. Nothing on the datalog showed the surge when it happened either, which leads me away from fuel and/or spark.

Cat puked on the TTA and all was fine and well till 10psi and wham the brick would move and block the exhaust, let off and it was fine lol

This is the only concrete thing I have found.

I actually got new injectors for it and installed. Distrib is from last nov or dec, swapped modules out. Ignition coil would show up on o2 if it was the cause, BLM are neither rich nor lean. All other sensors are within spec and the IAT and temp match when cool, etc........ Vacuum leaks are nil with it being 20inch at idle. 20n inch w/ .5 variance also rules out any internal engine issues also.

Also the exhaust doenst sound right, the harder I lay into it the more hooverish it sounds, when I drove back here after summer break, I stopped at a rest area. Restarted car with door open and I swore I had an exhaust leak like it was pushing out at the manifold, that has gone away then, but the exhuast doesnt sound right.

Idle is mostly normal, but under load, it doesnt sound right, even one of my school friends commented when we took it out to eat sun. Also when I noticed the surge that wasnt there prior.

It basically has had the same issue since I got back but its getting worse as time passes, so is the nasty sounds I have heard exhaust wise.

Im about to order the damn cats but its gonna nail me for $400 for the assembly. Would just get a couple, but by the time I have someone cut and weld it(nicely like I would do it) it will run me $300 at least Im betting. Dont want to bs it with hangers and clamps if I dont have too.

I really hate when I can fix anything, when it doesnt belong to me :-( yet my own cars screw me

later
Jeremy

 

A dead cylinder that has the injector connected still will burn up a cat in much less than 1100 miles. 10 miles can do permanent damage. 100 and it's toast.
If the vacuum at no load at high revs is higher than normal vacuum, it's a good chance the cat is blocking something.
Surging could be excessive EGR from the blockage.

 

Not to Hijack, but is this something that could be intermittent? The reason I ask is my car has the same problem, but I have a single cat and it seems to be random. I have also recently replaced all injectors. When it does run good it runs better than ive ever seen it run

 

i had a cat come apart on my car about 2 years ago, it ran fine at low RPM but had nothing past about 2500. the vacuum looked pretty much normal, even when it was up around 3000 RPM. it was just that one side of the motor couldn't exhale.
for the time being you could pull the cats & have a look in them, if the brick is melted in one, just knock it out & put it back on & see if that takes care of it.
or you could put on straight pipe in place of the cats as a test. 4 clamps, 2 pieces of pipe, probably about 20~30 dollars & put a new set of cats on later when you can better afford it.

i know what you mean about repairing everyone else's car, but not your own. if you ever saw my monte & knew that i know how to do paint & body work, you would laugh. other than the paint & 4 or 5 pieces of trim, i have every part i need.
and of course my wiring is a nightmare too. i spent about 5 hours last friday chasing down some damaged wiring on a 2001 Dodge Stratus, other than the new tape & new wire armor it looks just like factory, i wish i could say the same for my car.


PurpleHaze92, it could be, if the brick is partly melted & can move around. but normally you would hear it rattling.

 

Would it sound like the exhaust was rattling against the floor pan? If so perhaps I should change mine.

 

New cats are on there way as of teus morning.

Drove around with windows down beating the heck out of it, definitely something choking a bank like I found with the higher map readings.

So they should be here early next week I pray and hope, trying to not drive much until then.