kidzip

I've got a 93 with 44k miles on it. Mods include a tkt package from Petit and a downpipe. Last week I noticed that the car was flattening out at 6-6500 rpm and bucking. It accelerated to redline in first and second but in third at 6k rpm it would flatten out. Finally checked my boost gauge and noticed that the boost was spiking to 15psi. Drove the car home and filled it with gas. Left the station and the thing is hesitating and making a lot of noise. Parked it overnight and when I started it a lot of white smoke and the smell of gasoline. Popped the hood and got a strong smell of gasoline and the engine just lurching back and forth at idle. The firewall engine ground was disconnected from all the lurching so I connected it back but no improvement. If it is the MAP sensor how and where do I check it? If its blown can i drive it 150 miles to PETIT for a new ? Help! Spark plugs just changed less than 1k miles ago and the dealer says that the wires look fine. mkaufman@cfl.rr.com

Mahjik

iTrader: (1)

That doesn't necessarily mean the engine is blown. However, with gas smell coming from the engine bay, I wouldn't drive it. I would have it towed.

If you can smell gas in the engine bay while the car is idling, that typically means a gas leak somewhere. Driving it could cause a spark and an engine fire.

Have it towed to a shop or to Pettit.

EstCstFlp

Sounds like o-ring failure... Is you coolant mysteriously disappearing? If it is then I'm pretty sure it is o-ring failure and that requires a new or rebuild .

mike

efiniracing

Do you have a boost guage? if so the boost guage should show inconsistant fluctuation if the is bad. However if the needle is steady your problem is most likely elswhere.

BrianK

as far as the map sensor goes, go here for an explanation and a pic: https://www.rx7club.com/forum/showth...ght=map+sensor

kidzip

I checked the MAP sensor and indeed the hose was disconeected from it. I recconnected it and disconnected and reconnected the battery to reset the ECU. The car idles better now but I will ahve to drive it and see. The appears to be a nipple next to the throttle body pointing to the floor by the firewall. It doesnt have any hoses connected to it and I am wondering if that is the blowoff valve. I cant find any other hoses loose so I dont know what it is. Thanks for all your help guys.

Nathan Kwok

Yeah sounds like it was the MAP sensor, however you also are hitting fuel cut. Do something about the boost spikes, either a ProfecB, dawes valve or bore out the wastegate pills, something. I'm not sure if your TKT package comes with an ecu, I don't believe the base package does. If not, make sure to keep boost at 10lbs max or you will eventually blow the engine.

kidzip

what is causes the boost to spike like that?

Nathan Kwok

Basically your TKT package improves the airflow in and out of the engine, which improves the efficiency of the turbos. The ECU isn't aware of this and its wastegate signaling is tuned for a car with less flow. A good analogy is think of the turbos as a person blowing through a straw. You tell them, blow air out 50% as hard as you can, and since you know how big the straw is, you should know how much air comes out the other end. Then suddenly without telling you, your friend grabs a bigger straw, well now its easier to blow more air out so 50% effort results in a lot more air. This spools the turbos more quickly than the ecu expects, so you get spiking.

kidzip

could spiking to 15 psi for just a few seconds in a low mileage well maintained engine blow an apex seal or a turbo? I am getting a clanking sound which seems to come from the turbos as I can hear it loudest at the air cleaners. The engine idles real rough at around 300-400 rpm and smooths out somewhat as I increase the idle but it still runs really rough and smells really rich. Do you think I blew the engine or maybe just fouled a plug? Do you think its safe to drive 15 miles to the dealer? thanks for the reply

Nathan Kwok

Generally a single momentary spike isn't enough to cause any damage, but something obviously went wrong. You can't "blow the turbos" with boost spiking, turbos usually die a slow death, but you could have thrown an apex seal . The safest bet is to get it towed to Pettit so they can properly diagnose the problem. The car is probably ok to drive to the dealer, but unless you already know ahead of time that they are competant, I'd go with Pettit. I don't recommend driving it 150 miles though. I highly recommend getting a shop manual so you can familiarize yourself with where all the hoses go and everything. I'm not exactly sure what hose you are describing, maybe the AWS? The "blowoff valve(s)", there are two, one called the CRV or charge release valve and the other called the ABV or air-blowoff valve, are located in front of the airbox next to the intake hoses. They look like little brown round things about the size of a silver dollar and have their own little hoses. Good luck and let us know what it turns out to be.

kidzip

The hose that was disconnected was at the firewall. I believe it was to the boost sensor (MAP?). I dont have a stock airbox anymore just the Petit intake. Does this still have a CRV and ABV valve? How do you know if you blew an APex seal? thanks again.

Nathan Kwok

The boost (MAP) sensor is indeed on the firewall so you have that one right. The Pettit intake still locates both blowoff valves in the same place. Your intake should look like the one in the picture, I have one of the blowoff valves circled there. The other looks identical. That particular example is vented into the atmosphere, yours might have a hose coming out both ends, but either way your problem has nothing to do with the blowoff valves so no worries there. The surefire way to tell if you blew an apex seal is to get a compression test. Your local Mazda dealer will be able to do this without screwing up, so another option is to drive it to the dealer and get that done. If you have good compression your problem is elsewhere. The minimum standard is 6.0kg/cm^2 or 85psi, with a maximum or 1.5kg/cm^2 pressure differential between the 6 faces. If you blew an apex seal you should have barely any compression on 2 or 3 of the faces of one (probably the rear...) of the rotors. So, an example of a blown motor (in kg/cm^2): 6.4, 6.5, 6.3 front, 4.0, 0.0, 0.0 rear, or something to that effect.

blackscorpio

I think you cad drive it 150 miles just stay off boost no hard accelerating and keep the rpm below 4000 if possible. Also you will want to change your plugs as all that gas probably fouled up your plugs pretty good.

JMarasco

If the engine is lurching around enough to disconnect hoses and wires, is it possible that the engine isn't connected to the car anymore? Check the engine mounts. Don't drive it if the engine bay smells like gas. A gas smell in the engine bay is not an engine problem per se, it's a fuel leak problem. Fuel and heat will always lead to fire. An RX-7 engine gets plenty hot enough if driven to cause a fire.

Turbos will not make a clanking sound at idle (they aren't spinning). If the engine is moving around then you could have any number of metal pieces clanking against each other. If the turbo fails it will either seize (and not turn at all) or start burning a lot of oil (white smoke from a cracked casing). Turbos should spin plenty fast enough that any metal on metal contact should be heard as a high pitched buzz, not "clanking".

Anyway, my $0.02.

John

kidzip

Its off to the dealer tomorrow . I hope my baby is still intact. Thanks for all the help guys. I'll give you all a heads up when I figure this one out.

kidzip

One thought. If I fouled the rear rotor plugs the engine would run rough and perhaps make the clunking sound right? I'm hoping that the plugs are just fouled. I'd hate to replace my motor with just 44k on it.

blackscorpio

It sounds like you MAP sensor came off. THIS IS NOT A BIG DEAL. Its a stupid little hose attached to a sensor on the firewall. Do a search. If you can push a hose on a nipple.. and remve and tighten a 10mm bolt u can fix it.... or if you reaally want to you can spend a couple hundred at the dealer. Please do a search on MAP sensor. Wont force you do dit it just trying to help u out.

Nathan Kwok

He already reattached the MAP sensor and cleared the ECU so thats not it . It could be the plugs, since the dealer has to take them out to do the compression test, why don't you go ahead and replace them then unless they're really new, hey, can't hurt .

flameone

i thought you had to disconnect the battery AND hold the brake pedal for a while to reset the ecu.

I Killed Tupac

30 secs

kidzip

I reset the ecu the right way and the sucker fired right up. I still am getting boost creep to 15 psi and I dont know the cause. thanks for all the info.

RX7Elmo

i'm glad you have figured out the reason why the motor was running bad. Just be sure to monitor your boost gauge. I wonder what made it run bad and have ot reset the ecu. Maybe the ECU hit some sort of safety/limp mode.

Boost creep happened because of all the airflow mods you have. You will have to port the wastegate, or get some sort of boost controller. There are tons of threads here that discuss this in great detail as well as numerous websites.