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Flat-top pistons?

 
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  #1 (permalink)  
Old 26 May 2012, 09:11 pm
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Default Flat-top pistons?

First off, I want to say thanks to everyone that posts here. With the info I found in this forum I managed to get a beat down 01 pt limited running somewhat normal. My wife recently lost her job and we lost our car due to being too far behind on payments. We borrowed some money from family and manged to pick up a the cruiser for $2000. Body is good. Interior was great. It only had as few issues. The guy I purchased it from was working on it, but was either stuck or he thought of it as a waste of money. The good news is, after 3 days and roughly $400, I've managed to get the A/C fixed, and all engine codes dealt with and no longer appearing during code check. So again, thank you to everyone that posts here. In the long run I plan to get the cruiser to it's roots and I know I'll be here more often looking for help...

So onto my first questions.

When I first got the car, the guy working on it said he had flat-top pistons in the engine. It's a "B" engine w/ EGR. He said the pistons were the reason for it having a rough idle. I called BS but ended up getting the car anyways out of desperation. Nothing any better in the area for the amount of money I had. I ended up replacing all spark plugs and wires (I found a rubber spacer on the first plug.. why??), the MAP/MAF sensor, put in an after market intake (the original intake and filter case had cracks in it and was generally in the way.), and a new intake temp sensor. Reconnected battery and only got a p1684.. All good so far. I then took it for a 30 minute drive up a few freeways and thru downtown to get some stop and go. The rough idle was gone for the most part. It was only there when going through downtown and stopping at lights. It was like a couple of small jerks forward and was idling at 500rpms. Applied gas and there would be a slight hesitation before accelerating. Could this be from the flat-top pistons?

Another thing I noticed when I had things taken apart.. I removed the bolts at the top of the EGR tube and I expected it to stay in position. It fell backwards... It was like the lower part of the tube was on a ball joint.. Should it be loose like that? The bracket was bolted all the way down.. Could this be a cause of the jerk/low idle at stops?

On a side note, using the A/C does not affect the idle.. this happens if it is on or off. Seems as though turning it on makes it better though. Go figure.
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Old 26 May 2012, 09:30 pm
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Default Re: Flat-top pistons?

First, back away from the guy who told you flat top pistons cause a rough idle. Don't go back to him....ever.

The rubber spacer on the first plug is probably the spark plug well seal. If it pulled out, you need to replace it. It stops oil from getting from the top of the head to the top of the valve cover. You might need to replace all four seals. Not sure if you need to take off the valve cover to do this. See picture below.

The new spark plug gap is .040in. What did you set your to when you put the new plugs in? The slight hesitation could be a bad injector or low fuel pressure.

The second picture below shows the other end of the EGR tube. It's possible that the bolts (A) holding that tube tight are loose and allowing the tube to move when you took the upper two bolts off.

P.S. to the forum.



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Last edited by CREWZIN; 26 May 2012 at 09:34 pm.
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Old 26 May 2012, 09:46 pm
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Default Re: Flat-top pistons?

Ok. So after my wife just went to BK, the car died at the intersection. She said there was rough idle and it just died. I check for code and I'm getting p1297 again. It's a new sensor replaced earlier today.. what gives?

The rubber spacer was on the ceramic part of the spark plug.

The plugs I put in were NGX Iridium. No spacing needed.

Last edited by dncwalk; 26 May 2012 at 09:50 pm. Reason: addition
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Old 26 May 2012, 09:54 pm
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Default Re: Flat-top pistons?

Was the new MAP sensor a Chrysler/MOPAR part or from an auto store. Out PT's don't like electrical parts from after market auto stores. If it was a MOPAR part, I can't tell you what's wrong with it. Check it over good and make sure it's seated well into the back of the manifold and the wiring harness is good and tight.

Don't know why you'd have a rubber spacer on the top part of the plug.
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Old 26 May 2012, 10:34 pm
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Default Re: Flat-top pistons?

The MAP Sensor is made by Standard. The pigtail could be an issue as the red tab doesnt actually lock onto the sensor. Also, could the EGR Valve be causing this and throwing a 1297?
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Old 27 May 2012, 06:22 am
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Default Re: Flat-top pistons?

Rule # 1 Use only Chrysler sensors.
PT Cruisers only like Mopar/Chrysler dealer sensors. Its a fact proven on this forum over and over again.
CREWZIN is the man to ask and he will help as much as he can
Good luck with your problem !
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Old 27 May 2012, 09:02 am
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Default Re: Flat-top pistons?

Anyone got info on the pigtail? What each wire is for and the proper voltages on them? Also where they connect on the PCM?
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Old 27 May 2012, 09:51 am
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Default Re: Flat-top pistons?

Figured out the pinouts. GRN/BLK is signal, BLK/GRN is ground, PPL/WHT is 5v.

Called a friend with a hand vacuum and we tested the old MAP and the new one I got. Both work fine. I back probed the pigtail while having the MAP sensor connected and the car running. At idle i was getting 2.4-2.6 on the signal line, the ground was 13.05, and the other wire was 4.97. Going to try smoking here soon to rule out a leak. I understand that the PT may not like aftermarket parts, but it shouldn't run the way it is and after the money I've spent the past few days, I'm broke for at least a week. So in the mean time, I'm going to try and rule out any other problems before getting a MOPAR sensor and EGR valve. Also.. where can I get a replacement EGR tube?
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Old 27 May 2012, 10:37 am
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Default Re: Flat-top pistons?

Have you looked at the tube to see if you do need a new one? How about those bolts on the picture I showed you? Everything tight?
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Old 27 May 2012, 11:56 am
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Default Re: Flat-top pistons?

Both Bolts A and B are tight. The tube is loose on the bottom like it's on a ball-joint.

Edit: I removed the EGR Tube and put it back on. No more movement from it when I put it back on.. went for a quick drive and still rough idle and got 1297 before I got back home.

Last edited by dncwalk; 27 May 2012 at 12:42 pm.
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