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replacing 3.1 to 3.8 ?


tunnal
05-10-2005, 02:35 AM
Is anybody have experience replacing engine 3.1 to 3.8 on tranny, I need any advise for hided problems. Is that work very difficult?
On 3.1 engine I cannot find reason, why the ignition timming every morning is too late and engine will not start, after I turn ignition too early, engine will start and I need turn it back or else engine jumping very badly and stops. And on idle gear it stops to after any 10-20 sec.
HELP!

LMP
05-10-2005, 08:58 AM
There is no practical way to install a 3.8 in lieu of a 3.1 . THe engine block is totally different so the mating transmission housing too. Even swapping the entire engine/transmission would need a complete remake of the electrical wiring due to the very different injection type (was the 3.1 of '95 still a throttle body injection? Nickei66 has the '95 service manual and would probably comment on this) and computer. So...this seems to be to "no avail".

THe symptoms as described are strange to me. Because of its very common occurrence, I would disconnect the EGR valve, tap on it so it seats closed properly..just in case, and this might explain some of the effects. If this EGR valve is of the linear positioning type, I think it needs power to close as well as open (no spring return) , so that might explain, possibly but I do not see the exact track, why it needs a "reset" with 2 ignition keystrokes....bizarre. Of course, some cues could be obtained from a code scan..and since this is OBD2, you need a scanner. BUt the more I think of it, the more it suits to suspect the EGR valve.

tunnal
05-10-2005, 09:47 AM
I have full complect, engine 3.8, wiring and computer to, even gearbox - full stuff! But, where is located the EGR valve on 3.1 engine? Diagnostics gives me code 43 (knock sensor) and I don't know what to do

nicke66
05-10-2005, 05:16 PM
I have full complect, engine 3.8, wiring and computer to, even gearbox - full stuff! But, where is located the EGR valve on 3.1 engine? Diagnostics gives me code 43 (knock sensor) and I don't know what to do


First, I agree with LMP. Changing the engine is enough with work, also changing the type of engine, is much more than enough with work... Without have been digging into it, I really do not think it could be worth it for a 2000 Euro-car, even if all parts are for free. I guess you have to replace a lot more than just the engine and the tranny with cabling/cumputer etc.

How about emission regulations in Estonia? Are you even allowed to change the type of engine?

The knock sensor can cause your problem, a knock sensor is used to delay the ignision timing if the engine is knocking.

I will email you the 2 pages about the 3.1 knock sensor in the manual as soon as I get my scanner to work ( a HP PCS950, it is saying: "warming up" for hours. Does someone know what can be the problem?)

(LMP:Yes, the 95 3.1 has the old TBI system. The 95 3.1 has not OBDII. I think it even has the early GM ALDL with 160 baud comunication protocol, used in many GM cars in the 80th. Maybe it is even possible to use the "paper-clip" trick? (get DTCs with flashing check engine light) The 3.1 has not a linear EGR-valve, it has the same type of 3-chamber valve used in early 3.8. The linear EGR valve used for 3.8 94/95 has a return spring).

LMP
05-10-2005, 08:08 PM
Thanks for your comments Nickei. By the way, as soon as your scanner works, I'd like to have a copy of the electric circuit with the linear valve.

tunnal
05-11-2005, 03:55 AM
The EGR valve is already blocked and yes, I used the paper-clip trick. I already change ignition coil in distributor, computer( brayn) under dashboard too, but nothing. Now I will change knock sensor or his control modul and will see, helps it or not.
(I am very houpless already...) Thank you for response!

LMP
05-11-2005, 04:21 PM
I think just disconnecting the knock sensor will produce a definite "no knock" condition, and would this refrain any temptation to retard the timing? YOu might have an error code of "failed knock sensor" though, but I think you have it already.....but may be a "failed knock sensor" will indeed by default cause a retarded timing, as nicke suggested.
In case this might help:
www.avigex.ca/xport/dtc43_31a.jpg
www.avigex.ca/xport/dtc43_31b.jpg

By the way, what is the mileage on that engine? There has been at least one reported case of slipped timing chain on this forum 'bout the 3.1, and this has a serious effect on timing...and if I understand "turning the ignition tooearly" as turning the distributor forward, then it looks like the same symptoms as a slipped timing chain....

tunnal
05-13-2005, 01:01 AM
Disconnecting knock sensor modul makes no differents, anyway I must turn the distributor on the morning. Warm engine starts very well, on idle gear the engine jumping, and drops rpm-s to stops. If I turn distributor a little more late, engine looks work fine and wount stop on ilde gear, but then is backfire in throttlebody, if I step on the gas - impossible to drive. Yesterday I replace this modul (KS) at one workind piece, but no differents too.
"...what is the mileage on that engine?" I dont know, but fat lot I think ;-) It's not original. That kind problem appear after changing cilinder head gaskets, all other works fine, but just the timming. Anyone cannot help me - it's very strange, even my friend, with very good skills mechanic is baffled.
I will continue beat about and write/read here.
(In estonia is all possible, it's like "wounderland" and especially "europ", i must change the red turnlights to the yellow...but I think yet...)

kc0kfg
05-13-2005, 01:02 AM
Back you the org question of the 3.1 to the 3.8 if you are going to even think about doing that just skip ahead and put a 5.7 into it the fiero guys do it all the time with stock transaxles why not in a TS?

good luck Brian kc0kfg

tunnal
05-13-2005, 02:46 AM
after I found the reason of the actual problem on old engine, i swap engines anyway. Ofcourse it's possible and I like to try this kind of experience just for fun :-)) But I must sell the old engine!

tunnal
05-16-2005, 12:58 AM
Help - help - help !!!
Still problem on cold engine! Timming looks too late for start. After turning distributor engine starts and I turn distributor back to old position and engine starts already normally, but wont stay , after about minute stops. ECM and Knock Sensor module are replaced, but no differents. Another, if timming is lately, the engine work stady, but impossible throttle - buffly backfire at throttlebody. On normal timming the engine work jumpingly, looks like any sparkplug perchance is not good, but goes forward very well.
I check the knock sensor modul but cannot find the sensor itself on 3.1 engine. Where is it located? And what else I can replace or check for finding that "glaring error". I cannot start swaping engines before that.
To LMP: the mileage is 115000. What report you mean about chain. And I dont think so, the problem appears after changing cilinder head gaskets and I cannot see logics between timming and gaskets :-)
I'm very forbearing and will continue look for.
(...and the headline is already a little wrong, mayby it need to by change?)

nicke66
05-16-2005, 01:10 PM
The knock sensor is located at the back of the engine, at the fire wall side.

T.J.Speeder
05-23-2005, 07:31 PM
Hi guys. I know you guys say is very hard to do and it's a lot of work. But i have thae same problem. I have a 96 grand prix w/3100 cracked block, and I have a 3800 seriesII form a 96 bonneville. Can someone give info step to complete process on changing wires, comp, and motor.
please help.

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