HappyHokie18

Hey guys, looking for some help on some hesitation issues I am having with my 2001 AP1. Some back story, I bought this car a few months ago with 143k miles on the clock. Went in and did a whole bunch of work on it (fluids, filters, brakes, had local s2ki member perform a valve adjustment and retainer swap, new spark plugs, etc.) since the old owner definitely neglected some of the maintenance. Everything seemed to be alright for a while. After a few weeks, I started noticing that it was breaking up about 5k rpm. Did some research, and seemed like it might be the MAP sensor. Cleaned it up and the connector, put a new zip tie on, and it seemed to help. Car pulled well up to 9k for a week or so before it started stuttering and misfiring again.

At this point, the car wasn’t throwing any codes. I figured to just order a new sensor and then should be good. Before getting a new one, the car started to misfire at idle and kicked out codes for “random misfire” and had pending codes for cylinder 2, 3, 4 misfires. This happened about 3 times, all within a few minutes of a cold start. Clearing the codes allowed the car to run fine for a few days. I then thought it might be clogged injectors not getting enough fuel to the engine. Given the state of some of the other parts of the car, wouldn’t surprise me to think that these would be all gunked up. So I ordered some new OEM ones. Before installing them, I figured to do a compression test and had to replace the spark plug tube seals. With a cold engine, all 4 cylinders were within 10 psi and all above 200. While I was in there, gave a few taps to the MAP just for good measure. After buttoning everything back up, the car seemed to run well and pulled strong to 9k.

3 days later, my injectors arrive and I figure to go in and swap out the old ones. I also performed an IACV clean for good measure. When I pulled the injectors, the area where it connects to the intake manifold was caked with gunk. Seeing that, I was sure that was my issue. Cleaned out as much as I could, installed the new injectors and figured my car would be in tip top shape.

Instead, now I am having major problems with hesitation and stuttering, especially in low RPM. Cold starts initially drop the rpm very low (even this morning it cut out) and then when pulling away in first gear I have nearly no power. The car will start to buck and kick, and feels like it’s just not getting fuel. Above 3k rpm it seems to improve and after the car warms up, it runs pretty well, even at low rpm. Note that at any time, hot or cold, the engine will rev fine in neutral. Issue only happens when there is a load on the engine. There are also no codes getting kicked up by the computer.

I am going to go in and pull the injectors and make sure that I didn’t foul up anything and ensure that I have them entirely cleaned out. Was also going to try and clean the throttle body. Any other suggestions on what could be causing this issue and what I could look at doing to fix it? Any advice is greatly appreciated

TL;DR – Issues with breakup and misfiring. Replaced plugs, did valve adjustment, replaced MAP, checked compression. After replacing injectors, car now struggling at low RPM when cold.

Shift9303

When my car had multiple misfire codes and most of the symptoms you've described it ended up being a bad coil pack in cylinder 2; don't forget to check them too.

twohoos

So you have the new MAP in there, correct?

Might try cleaning the TB-MAP air passage:
https://www.s2ki.com/forums/showpost...7&postcount=36
Remove MAP, add a few drops of rubbing alcohol into the cavity, blow it out w/ a bulb or soft compressed air; repeat two or three times.

Were you careful not to dislodge any gunk when you cleaned the IACV? It's tempting to be a perfectionist, but you can end off worse than before - the buildup in there is very "dusty".. As Billman says, "NO CLEANERS! Just spin the shaft till it moves freely."

HappyHokie18

Not sure if it's the coil packs. Haven't had any issue with misfires since doing the compression check. Might have been that a connector was loose or not quite seated right, but now the issue feels more fuel related than not going off. Guy who did the retainers and valves checked the resistance across them and they were all good.

HappyHokie18

Was planning to try and clean that passage. Just odd now that I'm not having trouble at high rpm.
I didn't take the motor off of the IACV when i cleaned. Just used some cleaner and some q-tips. Wasn't that dirty and my only idle problems are for the first 5 seconds of a cold start. But I got the correct bits and will go back and make sure the shaft is free.

Shift9303

You're right, rereading your OP it does sound like your symptoms evolved slightly. When I got my misfire codes my car had a very rough idle that was actually higher than routine while you seem to be experiencing the opposite. The ECU was probably raising RPMs to try to avoid stalling from the dead weight of cylinder 2. It also felt like I had no power, the throttle would be very hesitant and feel like it would begin to stall out when the clutch started to bite. The car would also feel like it would open up and drive "normal" after 4k RPM or so. I was told by the mechanic that this was because the inertia in the engine really picks up as the RPMs rise and helps smooth out the uneven firing caused by missing a cylinder.

Unfortunately I'm no mechanic or engineer, only relying on past experience. Sorry I couldn't be too much help. Hope you get things figured out.

HappyHokie18

So I went back and put in the old injectors and cleaned the throttle body. It's pretty much back to where it was before. Some slight hesitation and jerkiness at low RPM. There are a few moments, almost comes in bunches, where there is a delay between pushing the throttle and getting a response. Usually in low RPM, maybe a bit more in higher gears (3,4,5,6 under 3k). I also got a check engine light today. I expected it to be a misfire but it showed : P0172 "system too rich bank 1" and had a pending P0170 code. I cleared it and have driven about 30 miles since with no codes (pending or stored). I was thinking this might be due to the PCV, TPS or an injector could be stuck. PCV valve rattles when I shake it, check throttle position with my OBDII scanner which showed 5.5% to 89.8% with smooth transition between idle and WOT, and all the injectors were clicking. Really starting to scratch my head at this point. My next thoughts would be fuel pump or fuel regulator and less likely would be an o2 sensor. Any thoughts from anyone?

twohoos

Wouldn't this indicate you've isolated the problem? Injectors would also fit with the code you pulled.
Not trying to be a smarta$$, just having trouble following what you've changed/tried.

HappyHokie18

It's more so that the new injectors I tried must have had some issue (or I installed them wrong). Basically I went from old injectors to new injectors and got worse performance. Went back to the old ones and returned to where I was before. I'm trying to solve the jerky behavior I've had though from the beginning. Then the code was thrown today, which is new and I hadn't received before.

No offense taken, I know this is a bit over the place. Trust me, its been alot chasing everything

HappyHokie18