Hi All.

 

My car has started missfiring at higher rpm, anything above 4k. I have since cleaned the maf and ptu connecters, also reset the ecu. It got much better after cleaning the maf but still misfiring loads. I have read other posts that suggest the maf can cause this. Can the car be ran without the maf connected to test this thory or is it 100% needed?

how easy is it to bypass then?

not done it myself, but

 

http://300zx.co.uk/forums/showpost.php?p=506326&postcount=2

 

sounds very straightforward in comparison!!

Yeah that does sound like a good idea, now just need to find out which pipes are the input/output to the heater system!

Just got a phone call from the garage. They have fixed my exhaust but cant get behind the engine to fit a heater bypass. They also removed the glove box to have a look but they confimed the dash will have to come out.

 

Grrr (again)

 

Looks like im doing the bypass myself, can anyone help me by giving me some info/instructions on which pipes i need to join up.

 

Thanks, Ed

bump

At the back of the engine dude,there are two pipes going into the bulkhead,just loop a pipe to those,sorted!

BTW-Boldy changed his Auto matrix in 11/2 hours :wack:

trying to find pic now.

http://www.300zx.co.uk/forums/attachment.php?attachmentid=12925

Done it! Thanks all. I found this and it helped loads.

http://www.300zx.co.uk/forums/showthread.php?t=74525&highlight=heater

 

Just pulled the rad out for a deep clean and flush out. Front pipes are coming off tomorrow and new stat going in!

 

I found that the metal pipes at the rear were a little corroded, is it an engine out job to change them?

Right then!

 

I have put my stat and rad back in, bypassed the heater and no more leak!

holding 80c even in traffic and there is still water in the top of the rad after its cooled YEY!

 

However! It is still misfiring above 4k rpm. Its still intermittant and making full boost. sometimes its a definate misfire and sometimes just no power at all.

 

Moving a bad coil pack connector seemed to make a difference so i have just changed the pack and connector.

 

Not tested it yet but i also did a diag test on the ecu. I am getting errors 13 and 34.

 

I dont understand why im getting 13? Both my stock and aftermarket temp gauges work fine. According to my Greddy informeter the sender to the ecu works fine as well, gives almost the same reading as my other gauges on the 2nd sender.

 

So why am i getting code 13?

 

Also code 34 - shit!

 

I checked the connector that goes to the det sensor and one of the wires had actually broken. I removed the connector and soldered the wires.

 

Diaged the ecu again and got the same codes!

 

Does the ecu need resettng to clear the codes?

 

What does det sound/feel like when it happens? Are my pistons going to melt if i keep testing the car? At the moment it just feels like a misfire, can be a strong jerk if it just misses once through the range, doesnt backfire or sound different.

 

I have removed the + batt connection to reset the ecu, leaving it overnight.

 

Hopefully this will clear the errors (wishful thinking!)

 

Does this sound like det?

 

Wasnt that hot today and im running optimax, same at 8 and 12psi boost.

oh yes i have cleaned and dried my maf out. Just want to know if my car is actually detting and if i should be panicing or not!

 

Ed

I checked the codes again after leaving the batt off overnight and no errors! getting 55 now.

 

I think i was getting 13 due to messing with the sender before, 34 was solved by resoldering the wires on the connector.

 

Been to usc today, got stuck in traffic on the way back and it never went over 80c on my guage or on the readout from the greddy informeter connected to the ecu, that now reports 0 errors as well.

 

It is still misfiring tho, still only about 4k rpm, does it more at the higher boost. Somtimes will go all the way through the range, but mostly misfires.

 

An ideas?

 

Next week im going to swap my ptu, maf and maybe clean my fuel filter out.

 

Ed

Changed the maf and ptu today and the problem has almost completly gone!

 

Had a couple of small splutters in high boost but nothing major, yesterday would not go above 4k rpm on high boost 90% of the time.

 

I still think it is the maf (see the name of this thread)!

 

I'm going to change the ptu back to mine for the run home and then it will confirm the maf was at fault.

 

My next question is as my maf is faulty and heading for the bin can it be disassembled and cleaned/rebuilt?

Have you checked/replaced the sparkplugs ?

not yet but they are less than a year old and changing the maff seems to have cured it. I was going to change the plugs if the maf and ptu swap didnt help.

 

My new maf is on loan only so need to try and repair mine, i took it off before and blew warm air through it with a hair dryer. Seemed slightly better but still really bad.

 

Is there a good way to service/repair the maf?

Ptu changed back - still running well!

 

As my above post, can the maf be repaired?

 

Ed

OK since the maf sarga I changed it and made a splash cover to stop the air filter getting wet. Car runs well on low boost but still misfires on high boost.

 

Can someone post up mickyb's number so I can get him to sort it out as im sick of it!

OK since the maf sarga I changed it and made a splash cover to stop the air filter getting wet. Car runs well on low boost but still misfires on high boost.

 

Can someone post up mickyb's number so I can get him to sort it out as im sick of it!

Contact details in his forum section bud http://www.300zx.co.uk/forums/forumdisplay.php?f=114

it could be the maf again as i only just jetwashed it! I didnt spray anywhere near the nose tho and its still ok on low boost, smooth and fast. I'll drive it to work tomorrow and see if its still the same.

it could be the maf again as i only just jetwashed it! I didnt spray anywhere near the nose tho and its still ok on low boost, smooth and fast. I'll drive it to work tomorrow and see if its still the same.

If its the MAF then you wont be able to rev past 2500-3000rpm.

Last time it would misfire above 4k rpm intermittantly and was down on power, it started after a heavy rain storm.

 

Changed just the maf and it ran fine, but still gave the odd mis on high boost.

 

Just overtook a mate, changed into 4th at 6800 rpm and all was well. Press the high boost button on the way back and got major misfire, switched it down to low and all ok again.

a misfire under boost or a juddering as it will feel is a classic symptom of a major boost leak.carry out a boost leak check.

nope, making full boost on both gauges.

 

I think its dett as i got code 34 again which i didnt have this morning